GWEN IFILL: We take you inside the historic Iran nuclear deal, to Vienna and Washington and back again, and then we break down the 2016 money game, tonight on Washington Week.

SECRETARY OF STATE JOHN KERRY: (From video.)

In return for the dramatic changes that Iran has accepted for its nuclear program, the international community will be lifting the nuclear-related sanctions on Iran's economy.

IRANIAN FOREIGN MINISTER JAVAD ZARIF: (From video.)

I believe this is a historic moment.

And it is an important achievement for all of us.

GWEN IFILL: From a moment of shared victory, to nearly instant criticism.

ISRAELI PRIME MINISTER BENJAMIN NETANYAHU: (From video.)

The world is a much more dangerous place today than it was yesterday.

HOUSE SPEAKER JOHN BOEHNER (R-OH): (From video.)

If in fact it's as bad a deal as I think it is at this moment, we'll do everything we can to stop it.

GWEN IFILL: With his legacy on the line - PRESIDENT BARACK OBAMA: (From video.)

Please have a seat.

GWEN IFILL: - the president is pushing back.

PRESIDENT BARACK OBAMA: (From video.)

For all the objections of Prime Minister Netanyahu or, for that matter, the - some of the Republican leadership that's already spoken, none of them have presented to me or the American people a better alternative.

GWEN IFILL: We examine what happens when history gives way to doubt.

Plus, a look at who's on first when it comes to money in the ever-more-crowded 2016 presidential race.

Depending on how you count, it may not be who you think.

Covering the week, Indira Lakshmanan, foreign affairs correspondent for Bloomberg News; David Sanger, national security correspondent for The New York Times; Michael Crowley, senior foreign policy correspondent for POLITICO; and Jeanne Cummings, political editor for The Wall Street Journal.

ANNOUNCER: Award-winning reporting and analysis.

Covering history as it happens.

From our nation's capital, this is Washington Week with Gwen Ifill.

Once again, from Washington, moderator Gwen Ifill.

GWEN IFILL: Good evening.

It took weeks, months, years, negotiating table spats and walkouts, physicists on call, politicians on edge, but the U.S. and its partners finally struck a deal this week on a far-reaching nonproliferation agreement that everyone at the table said means the end of Iran's nuclear ambitions.

PRESIDENT BARACK OBAMA: (From video.)

With this deal we cut off every single one of Iran's pathways to a nuclear program - a nuclear weapons program.

And Iran's nuclear program will be under severe limits for many years.

Without a deal, those pathways remain open.

There would be no limits to Iran's nuclear program and Iran could move closer to a nuclear bomb.

GWEN IFILL: Even before the ink was dry, critics pounced.

How would we hold Iran to its promises?

How extensive would those limits be?

And by doing away with punishing sanctions, aren't we rewarding enemies who still seek to do our allies harm?

ISRAELI PRIME MINISTER BENJAMIN NETANYAHU: (From video.)

They've gambled that in 10 years' time Iran's terrorist regime will change while removing any incentive for it to do so.

REPRESENTATIVE ED ROYCE (R-CA): (From video.)

President Obama has decided to place all his chips on the fact that the "death to America" chants will soon disappear.

This committee has to ask itself whether we are willing to roll the dice too.

GWEN IFILL: So it's complicated.

But fortunately for us, we have three of Washington's smartest foreign policy journalists at the table to help answer some of those questions - two of them fresh off the plane, practically, from Vienna.

Let's start by talking about how this deal came together, because this was not a foregone conclusion, was it, Indira?

INDIRA LAKSHMANAN: Not at all.

I mean, as you said, this has been going on for two and a half years, really, if you count it back to Almaty, Kazakhstan.

And there was no guarantee that this was going to finally happen.

And you know, we were there for 18 days straight of negotiations.

This was meant to be the final push.

And I think there were several days when it wasn't entirely clear whether this was maybe going to get bumped back to September.

I think, though, that John Kerry and his team realized that this was their moment and they were going to have to seize it, and it was going to be even harder to try to delay.

It wasn't going to make it any better.

And as he said many times, a deadline is a forcing mechanism.

And you know, we wrote stories, David and I both, about sort of what happened behind the scenes.

And there were incredible moments of emotion, including shouting at each other and saying, "Do you even want this deal?"

and threats of walkouts and a lot of drama.

And finally - GWEN IFILL: My favorite was, "Never threaten an Iranian."

INDIRA LAKSHMANAN: "Never threaten an Iranian," which became a hashtag with people showing, like, Persian kittens standing up on their legs - hind legs and things.

But, yes, I mean, all of that drama happened because I think both Iran and the P5+1 realized that this was their one shot - this was their shot to get the best possible terms they could.

They weren't going to be able to reopen it and renegotiate it and they had to push as hard as they possibly could now.

GWEN IFILL: So, David, when you finally got the agreement, what surprised you?

What were the surprise areas of agreement, as opposed to the disagreements we heard so much about leading up to it?

DAVID SANGER: Well, the surprise areas of agreement had been somewhat telegraphed at the previous session in Lausanne, Switzerland, where they got to most of the nuclear restrictions.

But the big surprise, I think, that Indira and I both saw when we were in Vienna was that in the end game some issues that came up that really had nothing to do with Iran's nuclear program.

So let me give you an example.

One of the nuclear-related sanctions imposed in 2006 during the Bush administration was a conventional arms trade ban on Iran.

They couldn't buy arms, they couldn't sell them.

And then a ballistic missile-related ban.

The Iranians said - INDIRA LAKSHMANAN: By the U.N., of course.

DAVID SANGER: And this was done by the United Nations.

And so the Iranians said, look, this is one of the nuclear-related sanctions.

So if we agree to everything else here that's got to come off with everything else.

Well, this was a big problem for Secretary Kerry, because if Iran both has an inflow of a large amount of money from the sanctions being lifted, and the ability to go buy and sell arms, it's going to inflame what's happening in Iraq, what's happening in Syria, Yemen, you know, Hezbollah and so forth.

GWEN IFILL: Well, before you go on, I want to listen - I want us to play a little bit of what Secretary Kerry said to my colleague Judy Woodruff today in Washington, talking about sanctions, and then we will respond on the other side.

DAVID SANGER: Sure.

SECRETARY JOHN KERRY: (From video.)

You have a choice.

Are you prepared to do what the U.N. resolution says, which is lift the sanctions over a period of time in return for their negotiating - where, by the way, they didn't just come to the negotiations, they have cut a deal - or do you want to go to war?

Because the alternative to this deal is they will do whatever they want, we will lose the sanctions, we will lose the support of the global community.

If the Congress of the United States turns this down there will be conflict in the region, because that's the only alternative.

GWEN IFILL: Michael, how much was riding on this for Senator - for Senator - Secretary Kerry?

He obviously was a senator, but he has to go back to those - to his former colleagues.

He's got to sell this.

And you can see, he's already in it.

MICHAEL CROWLEY: That's right.

Well, first of all, as a matter of his own personal legacy - we talk about the president's legacy.

Some things have kind of broken the president's way recently and you hear some people around him saying he actually didn't need this deal for his own legacy as badly as he might have because he's had kind of a good run, in our superficial calculation of these things in Washington.

John Kerry is a guy whose political career, dating back in the 1980s, has been hounded by the criticism that he talks a lot but doesn't have a lot of signature accomplishments, legislative achievements.

He won the Democratic nomination but not the presidency.

I think for him this means a huge amount.

But there is a real battle now, because I don't think it's a totally foregone conclusion that this deal will survive in the U.S. Congress.

I think the odds are very high that it will.

Congress can vote to disapprove it, the president will surely veto that resolution, and then Congress would need a two-thirds majority - a supermajority to override the veto.

But if you had some - you know, a dozen or so Democrats defect, they could uphold it and bring the deal down.

So what's happening now - the process isn't over.

There's a sales pitch underway.

And when you see the president in his press conference this week or you see John Kerry making the rounds of these interviews, they're trying to make a case to the U.S. Congress that says: This is the best it's going to get.

There's no realistic alternative.

You can't tear it down now.

We've gone too far.

And the alternative is much worse at this point, even as they are trying to reassure other allies in the region that this isn't as bad as you may think.

GWEN IFILL: Which is why you hear the president talking about the logic of the deal.

INDIRA LAKSHMANAN: Right.

MICHAEL CROWLEY: Well, and I was struck at that press conference - the story I wrote was focused on this - he - you know, I thought of his love for Mr. Spock which he has expressed, logic and science - the White House is coming really hard with the science on this deal, trying to make it seem as though there's really no counterargument at all.

And that drives opponents crazy, by the way.

GWEN IFILL: Well, what about the science of the deal, guys?

DAVID SANGER: Well, there's a reason that Ernie Moniz, the former head of nuclear physics at MIT and now the energy secretary, was brought to this deal, because there was a second negotiation going on that in some ways was more fascinating than the one between Secretary Kerry and Minister Javad Zarif, the Iranian foreign minister.

And that was between Moniz and his counterpart, his Iranian counterpart, who also went to MIT as a student.

And that conversation was an effort to depoliticize the issue by coming up with technical solutions to what was essentially a political problem.

And they managed to do it, much of it down in the wine cellar of the Coburg Palais Hotel, which was down so deep in the rocks, this old site, that the Iranians began to call it Fordow, which is the name of their underground nuclear enrichment center.

(Laughs.)

GWEN IFILL: Oh!

MICHAEL CROWLEY: And how many bottles of wine were down there?

DAVID SANGER: Sixty thousand.

INDIRA LAKSHMANAN: I don't think any of them were consumed during this negotiation, though, let's not give people the wrong idea.

But it did look like a dungeon down there.

DAVID SANGER: It did look like a dungeon.

And we were told definitively there is no wine in Fordow.

But there was plenty of radioactive material, which all has got to come out under this agreement.

But the idea here was take the politics out.

The problem is that when this goes to Congress, if your vision of what the deal was going to be was take apart all of Iran's nuclear facilities, dismantle everything, there's nothing that Ernest Moniz can say to you that you're going to like.

GWEN IFILL: Well, and there you go.

The accountability of Iran seems to be the sticking point, not only at that table, but also here.

How do - how do they reassure - is it possible, I suppose, for the administration to reassure anybody that Iran will be accountable to this deal?

INDIRA LAKSHMANAN: Look, I think the administration needs to do a better job of explaining why this deal is not great for Iran.

It's not a gift to Iran.

Because the other side has been able to sort of appropriate this agreement in saying this is a gift, all the sanctions are being released, they're allowed to enrich, you know, it's not - it's not good.

They could turn that argument on the head and say, wait a second, you know, they're reducing by two-thirds the number of centrifuges.

They're keeping this low amount of uranium that's enriched.

And they're going to have constant really invasive inspections by the IAEA.

And there's been this whole controversy that has arisen just in the last couple days about this 24 days - that Iran will have 24 days if there's a suspect site.

And the Obama administration needs to explain, hey, look, that's on top of the so-called Additional Protocol.

This is extra.

Otherwise the arguments could go on forever.

GWEN IFILL: This is what Susan Rice said to me the other night on the NewsHour, and it's what they've all said, which is, well, we have these snap-back sanctions, which is now my new favorite word, snap-back sanctions, which means that once we prove that they are not sticking to the deal we can reimpose the sanctions we have partially lifted.

But it's not clear, at least to members of Congress, whether that would work.

MICHAEL CROWLEY: Well, David, I'll defer to you.

Quickly just I'll say, what fascinates me about how that part of the deal and some other things having to do with inspections were structured was the degree to which it was designed to prevent Russia and China from screwing things up, essentially.

I mean, they did do a decent job in the deal of creating, you know, mechanisms and joint commissions where all the votes are winnable without the participation of Russia, China and Iran.

INDIRA LAKSHMANAN: That's the U.N. sanctions.

But of course, the U.S. can snap back its own sanctions unilaterally if it wants to.

And the only question at that point is, are the European nations and Russia and China going to abide by U.S. secondary sanctions at this point?

And of course, they won't if they think that Iran is not really cheating.

But that's one really important point.

People talk about this gold rush back to Iran.

I think that's really premature.

I think it's a gold crawl because businesses know that these sanctions could come back any time and they don't want to take the risk right away.

GWEN IFILL: John Kerry actually made that point to Judy again today as well.

DAVID SANGER: That's right, they can.

And remember, the Iranians are not without options if the United States or the U.N. does this snap back because they would then be freed of their responsibilities under this as well.

So there's a little bit of a poison pill built into this.

But I think it is worth examining the question that Secretary Kerry brought up in that conversation with Judy, which is what were your other alternatives - and the president brought this up as well.

I'm not sure the only other alternative was war, but it is certainly true that if somebody took military action - the Israelis, for example, or the U.S., against the Iranian program, the internal intelligence estimates were it sets the program back three or four years, and then it goes deeply underground.

And you may never - you know, you can't bomb knowledge, as they say, so they would rebuild it.

The cyberattacks that the United States and Israel together did on Iran set them back maybe a year.

So 10 to 15 years isn't bad.

It's also not as good as permanent.

INDIRA LAKSHMANAN: And they're taking the gamble that over that 10 to 15 years, or they're believing that Iran will little by little open up, and that trade will help open up and bring Iran, incentivize Iran to come back into the fold of the international community, not be a rogue state, not do terrorism.

Now, that may be too optimistic.

It may not actually happen that way.

But in the meantime, they do at least have verification and means for making sure that Iran is keeping up its side of the bargain.

GWEN IFILL: Michael, you were at the presidential news conference the other day.

He went on - he was so anxious to talk about this deal that he started asking himself questions because he didn't trust reporters would ask what he came prepared to answer.

It was a different way of doing a news conference.

But one of the things that came up, which there was much commentary about because of the way the question was formulated but it's still an essential question, which is: What about the other things that were left on the table, or were never on the table, which is to say American hostages.

Why wasn't that ever on the table?

And does that still - how did it become an assumption on the part of people who watch these things that somehow there would be a deal for the release of American hostages?

MICHAEL CROWLEY: Well, to the extent there was an assumption among some people, it may have been a combination of wishful thinking and just the perfectly natural conclusion that if we're talking to the Iranians about these hard issues and there's going to be this very difficult political tradeoff that this would be part of it.

By this, just to clarify, there are three Americans who are imprisoned in Iran, I believe sort of in the judicial system who are being charged.

One of them - probably best known in this town, Jason Rezaian, who is a Washington Post correspondent in Tehran.

There is a fourth American, Robert Levinson, a former FBI agent who disappeared under pretty mysterious circumstances years ago.

And I don't think he's formally in the judicial system there.

Also, when the diplomatic breakthrough with Cuba was unveiled, there was essentially a swap of prisoners.

And so I think that set a hopeful precedent.

Major Garrett of CBS asked the president a very provocative question, implying at least from the president's point of view that the president was celebrating a deal that left these people - GWEN IFILL: He actually used the word "celebrating."

It wasn't just implied from the president's point of view.

MICHAEL CROWLEY: (Laughs.)

Well, and I'll say, I was sitting pretty much right behind Major Garrett, and the look in the president's eye was something fierce.

I mean, I was getting the secondary heat burning off of Major's face as Obama stared him down.

But you know, to wrap up my answer, I guess I would say the administration's position was we can't - it's like negotiating with ISIS.

We can't make concessions on the nuclear question because Iran is holding people unfairly in some cases - or all cases, maybe, de facto hostages.

That's rewarding hostage taking.

DAVID SANGER: You know, the central argument the president has tried to make here is let's assume Iran is going to be a malicious actor, or at least a malign actor, for the next 10 to 15 years, maybe as long as the supreme leader is alive.

We don't know who his successor would be.

If that's the case, you're better off with an Iran that can't threaten that it's a threshold nuclear state than one that is.

And so he focused like a laser beam on the nuclear.

And it is interesting that some of the opposition that's come up now are raising issues outside the nuclear arena, because that may tell you that they think that they don't have much of a ground on the nuclear side.

GWEN IFILL: Well, let's talk about how hard it's going to be, especially on Capitol Hill, by listening to a little bit of what Senator Bob Corker, who's the head of the Senate Foreign Relations Committee, had to say about the deal, at least when it first came out.

SENATOR BOB CORKER (R-TN): (From video.)

Over the next 60 days we're going to go through this in great detail.

We're going to have a thoughtful and deliberate process.

Those who believe that this truly is going to keep Iran from getting a nuclear weapon will vote for it.

Those who believe that that is not the case and the world is not going to be safer, and in some ways it may pave the way for them to get a nuclear weapon, will vote against it.

That's our responsibility.

GWEN IFILL: On one hand, on the other hand.

Where is the hand - I don't know how to put this - how is Lady Justice handling this today?

INDIRA LAKSHMANAN: Look, I think Senator Corker, if we take him at his word, is going to be open-minded and is really going to read the deal and listen to the administration's briefings on it.

I think there are other members of Congress who are not listening at all.

Really, they don't care what - GWEN IFILL: Including people running for president.

INDIRA LAKSHMANAN: Including people running for president who have prejudged that this deal is terrible without actually reading it or knowing the intelligence behind it or anything else.

They're going to find that out, but I still think they're not going to support it.

I think it's going to be a really tough sell to get approval for this, over 50 in the Senate.

GWEN IFILL: And briefly, part of the tough sell is because of Israel, which has been uncompromising in its pushback here.

MICHAEL CROWLEY: Well, absolutely.

And I think, you know, because many members of the public, I think understandably, haven't been following this in great detail and don't know what snap backs mean and the 24-day window, what they will hear is an argument about Israel.

I think a lot of this deal will come down to - a lot of this debate will come down to claims that one side or another is for Israel or against Israel.

It will further partisanize Israel as an issue on Capitol Hill.

But I think that's the frame through which a lot of it will flow.

And Prime Minister Netanyahu is not letting up, and I believe he's got another trip to Washington scheduled in the near future.

So that - GWEN IFILL: We can probably write that speech right now.

(Laughter.)

All right.

Michael Crowley, David Sanger, Indira Lakshmanan, thank you.

Now on to politics.

We got some eye-popping numbers from the presidential candidates this week.

I know some of you still think the campaign is starting too early, but tell that to the donors who made hundreds of millions of dollars' worth of contributions to the people in the running.

Including cash raised by outside groups, Jeb Bush leads the pack with nearly $120 million raised, followed by Hillary Clinton at nearly $70 million.

Republicans Ted Cruz, Marco Rubio, Rick Perry and Democrat Bernie Sanders round out the top six.

But take that super PAC money out of there and the numbers look a little different.

Bernie Sanders is number two to Secretary Clinton and way ahead in the percentage of small donations.

So Jeanne Cummings now, the political editor at The Wall Street Journal, joins me now.

What do those numbers that we just saw tell us about where this campaign stands right now?

JEANNE CUMMINGS: Well, what they tell us is that we're in for a long haul this cycle.

And it's not just the money, it's the size of the field, because people can go into Iowa, go into New Hampshire, win by a teeny, tiny margin, and get a great big headline.

What will be different, I think, this year is that people are used to winning, maybe, in the first couple of states and then they have a gusher of money come in.

That can happen, but we do have a few people in the race who've collected enough that that infusion of cash may not actually be able to help a candidate stay in longer.

GWEN IFILL: It feels, though, like the architecture of fundraising has completely changed now because the numbers that we're seeing now really aren't real until we see these super PAC reported numbers later on, right?

JEANNE CUMMINGS: That's correct.

And what's really important for everyone to keep in mind is that with the decision to put so many resources into super PAC that the candidate has given up a lot of control of their campaign.

GWEN IFILL: Which means?

JEANNE CUMMINGS: When I spoke with - they can't direct how they spend it.

So they can't tell them, you know, quick, we need help in this precinct, or we need ads over here on this message, we're changing tactics.

They have a lot of subtle ways and not-so-subtle ways that they can signal to the super PAC what they want it to do, but in the rush of a campaign those signals can be overlooked.

And I spoke with Kevin Madden, who was on Romney's campaign.

He had a super PAC, and he said at one point they had pivoted and they were aiming all their firepower at Rick Santorum, and the super PAC ad went up and it was targeted at Newt Gingrich.

So those resources, in their mind, were wasted.

GWEN IFILL: So let's talk about how they're spending all of this money.

They're bringing it in hand over fist, and Hillary Clinton for instance is raising a lot of money and she's spending a lot of money.

JEANNE CUMMINGS: She is, but she really is building an institution.

Hillary Clinton has the advantage of being, you know, 99 percent sure she's going to take the primary.

So right from the beginning, she could start building a general election campaign.

So big costs are just computer hardware.

She's buying lists.

She's buying - she has a big staff.

She - you know, and these people are in for the duration.

It is - it is funny to compare, though, to Bernie Sanders, who - GWEN IFILL: Well, that's what I was going to ask.

Should she be worried about him, who, you know, without super PAC money, is raising, you know, percentage-wise, a lot of money.

JEANNE CUMMINGS: He's doing - he's doing very well; $15 million is perfectly respectable in this arena.

But the thing about Bernie that's really interesting is he is very frugal.

He's only spent a couple million dollars.

And what he did when he went to get his office furniture, they went on Craigslist.

(Laughter, laughs.)

GWEN IFILL: So if you're Scott Walker, you just got into this race this week and didn't have to report what he pulled in.

But who is he competing against?

Ted Cruz is doing well.

Jeb Bush, obviously, is leading the pack.

JEANNE CUMMINGS: I see Walker in a very different category, and I think Walker's going to be interesting because I think he's going to bring a new group of donors.

Every cycle there's, you know, some new in thing or it people.

And you know, in the case of Romney it was Mormons and the Utah money, the old Olympic money.

In the case of Walker, I think we may see some new faces from the industrial Midwest and West who have not been particularly active in contributing to campaigns.

He may bring a whole different network in.

GWEN IFILL: And who's the network for Jeb Bush?

JEANNE CUMMINGS: Jeb Bush is relying upon the Bush network.

We looked at his - who gave to him, and there are tons and tons of associations with the two prior Bush administrations.

In addition, heavily out of Wall Street.

That's not a surprise.

He, you know, went into - on some boards after he was governor.

He's made connections there.

He got about $300,000 from Wall Street.

GWEN IFILL: And Hillary is presumably getting the women supporters and the celebrity, the Hollywood group.

JEANNE CUMMINGS: Yes, she is, and to the surprise of some maybe she's also getting Wall Street money.

GWEN IFILL: Really?

JEANNE CUMMINGS: Three hundred thousand (dollars) for Hillary.

GWEN IFILL: Why is that?

JEANNE CUMMINGS: Well, the Clintons have always been close to Wall Street, and may of her bundlers are from Wall Street.

GWEN IFILL: OK. Well, we'll be watching the way all of this shoots out because I get the feeling money is going to be defining this race even more than usual.

JEANNE CUMMINGS: Mmm hmm.

GWEN IFILL: Thank you, Jeanne.

Thanks, everybody, for hanging out with us in our temporary digs here.

We'll be home soon, I promise.

In the meantime, get your extended Washington Week fix later tonight and all week long on our Webcast Extra, where among other things we'll talk more about the key players behind the scenes of the historic Iran nuclear deal.

Stay up to speed every night with me and Judy Woodruff on the PBS NewsHour.

We're debuting a spiffy new NewsHour look next week.

And we'll see you right here next week on Washington Week.

Good night.