ARI SHAPIRO, HOST:
Right now, the leading Republican candidates for president are in the second hour of their latest debate. On a stage in Boulder, Colo., 10 candidates are debating economic issues and other matters. NPR political reporter Sarah McCammon is following the action and joins us now. Hi, Sarah.
SARAH MCCAMMON, BYLINE: Hi, Ari.
SHAPIRO: So going into the debate, we were waiting to see whether Marco Rubio, the Florida senator, would come under greater scrutiny since he's moved up in the polls lately. What have we heard from him?
MCCAMMON: Well, we saw a big clash with Jeb Bush, who he upstaged by passing him in the polls. Rubio's been criticized for his poor attendance record in the Senate. And here's how he responded tonight.
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MARCO RUBIO: I don't remember you ever complaining about John McCain's vote record. The only reason why you're doing it now is 'cause we're running for the same position and someone has convinced you that attacking me is going to help you.
JEB BUSH: I've been...
RUBIO: Here's the bottom line. I'm not...
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RUBIO: I can't pay you...
MCCAMMON: So as a Florida resident, Bush called on Rubio to resign in that CNBC debate on Westwood One tonight. We saw some serious fireworks between the two. Of course, Rubio and Bush are both from Florida, and Bush has been a mentor to Rubio. But that relationship has been strained as they're both running for the GOP nomination.
SHAPIRO: There was also a big moment from Texas senator Ted Cruz tonight. He attacked the media, which is always popular with Republican primary voters - no different tonight, hmm?
MCCAMMON: Right. It's been a common theme of his on the campaign trail. He often accuses reporters of trying to pit the Republican candidates against each other at the expense of talking about real issues. And tonight, he made that claim again, but he got really specific. Let's listen.
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TED CRUZ: Look at the questions. Donald Trump, are you a comic book villain? Ben Carson, can you do math? John Kasich, will you insult two people over here? Marco Rubio, why don't you resign? Jeb Bush, why have your numbers fallen? How about talking about the substantive issues people care about.
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MCCAMMON: So I think, Ari, what you see there is what a deft debater Cruz is and just how quick he is on his feet.
SHAPIRO: All right. Well, Cruz mentioned math there, and this is supposed to be an economic debate. How much math was there? Did the conversation really stick to economic policy?
MCCAMMON: Yeah. There was a fair bit of discussion about taxes. So several of the candidates are pushing flat taxes. Ted Cruz trotted out his new tax plan tonight as the debate was kind of kicking off. The candidates all seemed to be competing for the simplest, flattest tax plan possible. Carly Fiorina repeated something she's said on the campaign trail, arguing for a tax code that is only three pages long. She says that's as long as it can be for average people to understand it without having to hire a team of accountants. Ben Carson calls for a 15 percent-or-so flat tax and massive government cuts. Cruz's plan would be a 10 percent flat tax. And you know, John Kasich was kind of the one voice pushing back on all of this, just questioning how realistic these ideas are.
SHAPIRO: Well, one voice that you haven't mentioned much about - Donald Trump, often the loudest voice in the room in past debates. Coming into tonight, his lead was being seriously challenged for the first time by Ben Carson. Talk about the role that Trump played this evening.
MCCAMMON: Right. And Trump hasn't really been attacking Carson so much tonight. You know, GOP voters really like Ben Carson and his low-key, mild-mannered style, so Trump has to be a little careful about coming down too hard on him. But like all the candidates, Trump was asked about his biggest weakness. Here's how he responded.
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DONALD TRUMP: I trust people too much. I'm too trusting. And when they let me down, if they let me down, I never forgive.
MCCAMMON: And that, Ari, is actually quite similar to a warning he gave to voters in Iowa this week. That is where he's been slipping in the polls most noticeably. And while he was in Iowa, he said if he loses that state, quote, "I will never speak to you people again."
SHAPIRO: Well, then, Sarah McCammon, I'm sure I will speak to you again. This is many months to go yet on the campaign.
MCCAMMON: Same to you.
SHAPIRO: And thanks for the coverage.
MCCAMMON: Thank you.
SHAPIRO: That's NPR political reporter Sarah McCammon. Transcript provided by NPR, Copyright NPR.
