ANNOUNCER: This is the Washington Week Webcast Extra.

GWEN IFILL: Hello, I'm Gwen Ifill.

Welcome to an extended edition of our Webcast Extra.

I'm joined by Dan Balz of The Washington Post; Jonathan Martin of The New York Times, who just put his phone down; and Molly Ball of The Atlantic.

Busted.

(Laughter.)

This has been such an eventful week that we didn't get to a lot of it in the regular weekly broadcast.

Luckily, we'll pick up where we left off.

Let's start with the Democrats, who seem to be happy to keep their heads down lest they get hit in the Republican crossfire.

Hillary Clinton is going for lofty and Bernie Sanders is going for her.

FORMER SECRETARY OF STATE HILLARY CLINTON: (From video.)

I believe deeply that if we resist the forces trying to drive us apart, we can come together to make this country work for everyone - the struggling, the striving and the successful.

SENATOR BERNIE SANDERS (I-VT): (From video.)

She was very, very wrong, and millions of families around this country have been suffering as a result of those disastrous trade agreements.

GWEN IFILL: Trade agreements was what he was saying, even though he seemed to tail off there at the end.

He's attacking her, but without a lot of gusto.

But what exactly is Sanders' plan for derailing Hillary Clinton at this late date, Jonathan?

JONATHAN MARTIN: It's not very easy.

She has a wide lead in delegates, in part because of her command of superdelegates.

A smart Democrat pointed out to me this week that the Republicans did Hillary a huge favor by changing their calendar and basically frontloading the calendar with all of those states in the South.

The idea was to give their sort of regional base a real voice in the primary in the way that they hadn't had after years of Iowa and New Hampshire.

But in doing so, they enabled all of these states with heavily black populations to also vote first, and in doing so they came in big for Hillary.

And that effectively is what saved her candidacy.

And so that's a sort of great irony here, is that that was caused in part by the GOP.

So from now, how does Sanders catch up?

It's not easy to see.

This is proportional all the way through.

There's no winner-take-all element at all.

I'm not sure how it happens.

GWEN IFILL: Let's look at the delegate count.

Let's look at the delegate count for Democrats.

They need 2,383 delegates for the nomination.

Hillary Clinton currently has 1,058.

Bernie Sanders has 431.

And as you pointed out, she's got a huge advantage.

DAN BALZ: Well, she is in the position that Barack Obama was in the position eight years ago, which is to say she has a lead in pledged delegates.

Put aside the superdelegates, because in a sense - GWEN IFILL: Which is part of that number.

DAN BALZ: - which is part of that number - because the Clinton campaign doesn't want to overplay that because it looks like the establishment crushing the insurgency, and - GWEN IFILL: Which it kind of is.

JONATHAN MARTIN: Which they are.

DAN BALZ: Which it is.

(Laughter.)

MOLLY BALL: They would be, if she weren't ahead in regular delegates.

But she is.

DAN BALZ: Right.

But she's got a lead in pledged delegates, and given the rules of the Democratic Party, unlike the Republicans, who have winner-take-all primaries, the Democrats don't.

It's all proportional.

And it's very difficult to see Sanders winning enough states with a big enough percentage to actually catch up in those delegates.

MOLLY BALL: Well, the macro problem for Bernie Sanders is that he is not winning over minority voters.

Now, this is something his campaign thought he would be able to do.

They're spending a lot of money on advertising.

They really thought that, like Obama in 2008, Bernie Sanders was an unfamiliar face to a lot of people in the base of the party, but once they found out about him they would get excited about him.

That is not happening in particularly African-American communities.

GWEN IFILL: There's kind of a big difference.

MOLLY BALL: There is a big difference.

I'm glad you pointed that out.

JONATHAN MARTIN: Smart.

(Laughs.)

MOLLY BALL: But I think the problem for him is not just about math, not just about states, not just about voting blocs.

It's a larger sort of psychological problem, particularly in the era of Barack Obama.

You cannot be a credible nominee of the Democratic Party if you do not attract minority voters.

It just doesn't make sense.

GWEN IFILL: Well, and especially - MOLLY BALL: It doesn't win you a general election, but it also just is the wrong fit for this party, that is increasingly the party of minority votes.

So - GWEN IFILL: Well, and the party of liberal voters.

So one thing that has been clear is that he is trying to play to the fact that more liberal voters are engaged in this, and not only by talking about, you know, the Keystone Pipeline and talking about bad trade deals, but also now, belatedly, coming around to reminding people what bothers them the most about Hillary Clinton.

And that's where the email controversy doesn't die and keeps reinforcing that argument.

JONATHAN MARTIN: But it doesn't bother rank-and-file Democratic primary voters all that much.

And you know, the more ideologically driven ones will be for Bernie, but for a lot of other ones they have a(n) attachment to the Clintons and they like them, and they're going to be for them.

DAN BALZ: One of the arguments - excuse me, go ahead.

MOLLY BALL: Oh, I was just going to say one of the things that the Sanders campaign is hoping is that black voters in the South may be different than black voters in other places.

A lot of the Rust Belt states that are coming up also have very large African-American populations.

Now, you know, African-Americans in the South are going to be more rural, older, more socially conservative.

GWEN IFILL: But do they understand that many of the African-Americans in the North came from the South, or their parents or their grandparents came from the South, and still have roots there?

MOLLY BALL: Absolutely.

GWEN IFILL: It's not - I don't think the geography works in - JONATHAN MARTIN: It's a tough sell.

MOLLY BALL: Well, I'm just saying that that's - that is something that they are hoping for that we have yet to see.

JONATHAN MARTIN: Can I make one fast observation?

We were talking earlier about how the Republican race has kind of transcended the traditional divide, how Trump has sort of been something that sort of supersedes the establishment versus hard right because he's someone totally different, he's post-policy in some ways.

As different as that race has been, the Democratic race has kind of returned to form of the Democratic primary structure that we've seen now for decades, where you have an insurgent liberal who for a while gets hot, who picks up a lot of steam, becomes kind of the beau ideal of the college campuses, and especially people who are passionate about economic inequality and national security, but then comes back down to earth and they can't expand their base to include non-white voters.

How many times, Dan, have we seen that same narrative play out?

And Obama was different in a way, of course, because Obama was able to appeal to African-Americans.

But here we go again, it's Jerry Brown, it's Paul Tsongas, it's Bill Bradley.

GWEN IFILL: Howard Dean.

JONATHAN MARTIN: Howard Dean, you name it.

DAN BALZ: Even Gary Hart.

JONATHAN MARTIN: Gary Hart, yeah.

GWEN IFILL: It should also be said that Barack Obama appealed to white voters, too, and that was - JONATHAN MARTIN: That was the key.

It was both, yeah.

DAN BALZ: One other problem for Sanders is - as he pushes forward is his argument about why he would be a stronger general election candidate is that he will bring out more voters, that he can attract a bigger coalition.

But in the primaries, the turnout for the Democrats has not been strong.

It is lower by far than it was in 2008.

So his credibility on that is in question, about whether he has a coalition that's really going to come out and surge.

GWEN IFILL: Go ahead.

One more thought, yeah.

MOLLY BALL: I would just say - I would just say that we should not - that's a very good point, but we shouldn't undersell how disruptive this primary has been for the Democrats because I think if someone - you know, you could have said what you just said six months ago and someone would have said, oh, that's why Martin O'Malley is going to be the last man standing against Hillary Clinton.

And I don't think anyone expected that it would be Bernie Sanders, and I think that the liberal alternative to the establishment candidate in Democratic primaries has usually been a sort of reform candidate, not a radical.

And the fact that Bernie Sanders is a radical is telling Democrats something they didn't know about the temperament of their base.

They didn't think their base was this riled up.

GWEN IFILL: But there's still a danger in a protracted primary for Hillary Clinton, isn't there?

MOLLY BALL: Well, it worked out OK in 2008.

And you know, at this point the Clinton team doesn't seem to be sweating Sanders too hard.

Now, if she starts losing, if we see the momentum turn, certainly they will.

At this point, they feel - you talk to them and they say we expect he'll be in for a while, he's got a lot of money.

DAN BALZ: Yes.

MOLLY BALL: He's got a lot of money.

But as long as she keeps winning - you know, and they're going to keep doing debates; she's not ignoring him - but they're feeling pretty good.

DAN BALZ: The other aspect about a protracted fight is one thing we know about Clinton as a candidate is that when the focus is almost totally on her, she runs into trouble because she gets measured against some ideal of what she ought to be.

I mean, it's helpful in some way for her to have an opponent who she can probably beat without, you know, a lot of difficulty.

GWEN IFILL: Sweating too much.

DAN BALZ: Yeah.

GWEN IFILL: Except she's got to start raising money again.

OK, let me - since we have an extended webcast tonight, I want to go back to the Republican story, which has gotten us so captivated.

This civil war that we are seeing break out has had a lot of unusual qualities, and one of them is that a sitting U.S. senator this week said he wasn't interested in voting for Hillary Clinton, but also not interested in voting for Donald Trump if he was the nominee.

Let's listen to Senator Ben Sasse of Nebraska.

SENATOR BEN SASSE (R-NE): (From video.)

If you got to a place where those are the two major-party nominees - and I certainly hope that they're not - I'd have to look for a third-party option.

JAKE TAPPER (CNN): (From video.)

Do you have somebody in mind?

Is there somebody you would - SENATOR BEN SASSE (R-NE): (From video.)

No, but I believe that there will be more candidates that enter this race if the only choices that we get are two dishonest New York liberals.

GWEN IFILL: What does Ben Sasse know that we don't?

Back-channel negotiations going on, a plan, someone who they have in mind?

MOLLY BALL: I think he's being honest.

I mean, I know Ben Sasse.

He's a very interesting character, sort of a Tea Party intellectual, and I think this is sincerely where he is.

You do hear - you do hear voices on the right saying maybe we can co-opt a third party, whether it's the Libertarian Party, the Constitution Party, one of these parties that has ballot access in most of the states, because that's the obstacle in most cases to an independent or a third-party run, some just saying they'd sit it out to teach everybody a lesson.

But you know, the Republicans are separating into camps on this because you have one senator who said he wouldn't vote for any - for Trump or for the Democrats, but you also have Jeff Sessions, who's endorsed Donald Trump.

So there are also Republican officeholders who are coming around to Trump.

And you know, several members of Congress, two sitting governors and another former governor have endorsed Trump.

So it's going to be interesting to see which camp gets bigger.

JONATHAN MARTIN: And that's the danger for the establishment, is that winning begets winning, but it also begets a sort of, I guess you could say, you know, finally coming to terms with the fact that he is going to be the nominee.

And if you see Trump win big on Tuesday in Michigan and Mississippi, that will probably prompt more endorsement.

And the following Tuesday, if he wins in Ohio and Florida, the floodgates will be open and you'll see a lot of people hopping on board the Trump train.

DAN BALZ: Perhaps.

I mean, I don't disagree with that, but I don't think it solves the problem of what is the identity of the Republican Party with Trump as the nominee.

JONATHAN MARTIN: Oh, I agree with - totally agree, yeah.

DAN BALZ: And I think that battle continues, and you will see people trying to figure out if you're - you know, if you're running for the Senate and in a tough race, how you position yourself vis-a-vis Trump.

You will see fighting underneath him for the future of the party because a lot of people will think, well, he's going to get beat.

So it's - I mean, it's a period of turmoil that's not going to easily be resolved, even under the scenario I think that you're fairly describing.

JONATHAN MARTIN: There was some small solace for Capitol Hill Republicans this week when, looking at Texas and Alabama on Super Tuesday, there were some closely watched House and Senate primaries, and the concern among the establishment was, well, are our people going to get sucked into the Trump undertow?

And, for example, longtime Senator Richard Shelby from Alabama had a primary.

There were a couple House races in Texas of veterans.

And they all survived.

And so I think there is some hope on the Hill, at least, that this is a Trump phenomena entirely and this is not going to impact us.

GWEN IFILL: And they don't be dragged down.

JONATHAN MARTIN: Yeah, down ballot, yeah.

GWEN IFILL: OK. Well, thank you, everybody.

We could go on, but we won't.

But stay online at PBS.org/WashingtonWeek, where you will find the answer to a question so many people seem to be asking.

For some reason, they're asking what would it take to move to Canada.

And we'll see you - we have the answer.

And we'll see you next time on the Washington Week Webcast Extra.