GWEN IFILL: Before the president presents his policy prescriptions tomorrow night, eight Republicans seeking to replace him get their turn tonight. The setting will be a debate staged at the Reagan Presidential Library in Simi Valley, Calif.
For a preview of tonight's face-off, we turn to NewsHour political editor David Chalian, who is not in California, but right here with us.
David, we're looking at eight people on the stage, but we're really only paying attention tonight to two.
DAVID CHALIAN: That's right, Mitt Romney, who was the front-runner and is no longer, and Rick Perry, the governor of Texas, who now is the front-runner in this race, has only been in this race for about three-and-a-half weeks, Gwen.
And the race is shaping up into this two-man race. Even Michele Bachmann's former campaign manager said as such. He's no longer the campaign manager after saying that. But it is true that this dynamic -- I am so fascinated to watch how Romney responds to Rick Perry as a new front-runner, because Mitt Romney is in a very new role tonight.
GWEN IFILL: Yes, because Mitt Romney has been the front-runner up until this week's clutch of poll which show Rick Perry vaunting over him.
So what does he do with that different role?
DAVID CHALIAN: Well, so the way he had been handling it, right, was to play sort of that Rose Garden strategy that a front-runner likes to play. Stay above the fray. He's been keeping his focus very much on President Obama, not really engaging his Republican opponents so much.
That's not going to work anymore. This is an opportunity tonight for Mitt Romney to start contrasting himself with Rick Perry. But you have to remember, Rick Perry is still not widely known. I know he's been governor of one of our largest states in Texas for 10 years, but there are still a lot of people across the country who don't yet know him.
So while Rick Perry is going to be sort of trying to introduce himself to a larger public, he's got Mitt Romney and six others on the stage who are going to be throwing their slings and arrows all towards him because he's the one wearing the big target.
GWEN IFILL: Have we seen him enough in settings like this that we know kind of debater Rick Perry would be? We know what kind of stump speaker he is, but this is a very different kind of situation.
DAVID CHALIAN: Well, we do know that he's an aggressive candidate, whether in previous debates during his Texas gubernatorial campaigns or, as you said, out on the stump. This is not somebody who shies away from a punch.
His campaign even yesterday when Mitt Romney delivered his jobs plan in Nevada issued a very aggressive statement cutting down the plan. So I don't think this is somebody who's going to shy away from drawing contrasts with his other opponents.
His campaign, of course, is trying to lower expectations. That's the name of the game for these debates. And they're trying to say, oh, he hasn't had so many debates. He's certainly never been in a big national debate like this.
That's all true, but this guy has been governor of Texas for 10 years, has been in politics for a long time, and knows what this kind of forum is like.
GWEN IFILL: You mentioned Mitt Romney's economic speech yesterday. Jon Huntsman gave one last week. And we're expecting the president's tomorrow. Are we expecting to hear any of that topic tonight? Is that going to be the main topic?
DAVID CHALIAN: There's no doubt that all of the candidates on the stage tonight are aware that the president's speech is tomorrow night and see this as an opportunity to call on the president to enact policies that, of course, the president's not interested in enacting. This is a Republican debate.
I do think that we're not going to see Rick Perry deliver tonight on the debate stage his economic plan. He is brand-new to the race. He has not been speaking in specifics at all on the campaign trail. It's been much more sort of broad philosophical differences he has with the president.
So I don't think you should expect to see that you can contrast everything said tonight with the president's plan tomorrow night, but I do think you're going do see some candidates try to -- for instance, Jon Huntsman, he is going to try to draw out a more moderate position here, try to reach out to those independent voters, show why he could go toe to toe, why he thinks he could go toe to toe with Barack Obama in a general election.
GWEN IFILL: It wasn't that long ago that Michele Bachmann had her big breakout moment when she announced from the stage of a debate that she was in the race. And then she went on to win the Iowa straw poll. And now this week's poll shows her pulling up a distant third. What does she have to do tonight?
DAVID CHALIAN: Not just a distant third, Gwen. Her support has been cut in half. In July, she was at 16 percent in the polls. She's at 8 percent now. All of that support fled to Rick Perry. So she's in real trouble because she has to find a way to reignite that Tea Party support she had.
All those Tea Party supporters have gone the way of Rick Perry. She needs to prove relevance tonight, is what her mission is.
GWEN IFILL: Are there non-Tea Party voters who any of them are trying to get tonight? We know that they're all trying to split up -- that they're all fighting over the same poll of voters -- little pool of voters when it comes to the most conservative members of the Republican Party, but what about everybody else?
DAVID CHALIAN: That's a fantastic question.
And it really comes down to general election viability and electability. And this is why -- this is the one number in the recent polls that I think has Mitt Romney most concerned. ABC News/Washington Post poll, when asked among Republican voters who do you think has the best chance to beat Barack Obama in November 2012, 30 percent of them say Rick Perry now; 20 percent say Mitt Romney.
That is the number that Mitt Romney needs to change. His deal tonight, his task ahead of him is to try to talk to a broad swathe of Republican voters, not just the Tea Party, to say that he's the most electable come November 2012.
GWEN IFILL: And the reason he needs to do that is because, all of a sudden, the president looks truly vulnerable toll this group. So are we going to -- we have seen in past debates in which they all agree that Obama has to go.
Do they start getting, described them -- taking shots at each other themselves -- instead and leave a president -- the president to go above the fray?
DAVID CHALIAN: I don't think the president ever gets to be above the fray in a Republican debate.
GWEN IFILL: No.
DAVID CHALIAN: I do think that -- especially one sitting at 38 percent, 39 percent, 40 percent in the polls, he's a pretty easy target.
And that's partisan red meat that they need to sort of hand out to -- dangle out there to their most partisan supporters. But there's no doubt that we're in this post-Labor Day phase now. It's a higher level of engagement. There is this new front-runner in the race. And we're going see each of these Republican candidates start differentiating on their records, on their past statements, and not just hitting the president.
GWEN IFILL: David Chalian, I know what you will be doing tonight. I will be doing it, too. See you later.
DAVID CHALIAN: OK.