AUDIE CORNISH, HOST:
Republican presidential candidates are back on the campaign trail after debating last night in Las Vegas. It was the first Republican debate since the attacks on Paris and San Bernardino. The candidates sparred over domestic surveillance, immigration and ways to defeat ISIS. Now they're trying to convince voters that they're on the right side of those arguments. NPR's Sarah McCammon was with one of those candidates, Senator Marco Rubio, today in Manchester, N.H. And, Sarah, Rubio was central to one of the big kind of debate battles last night which was over the now-defunct program to collect bulk data on Americans' phone records. How did he talk about that today?
SARAH MCCAMMON, BYLINE: Well, Rubio is trying to make the case to voters that he has the most well-thought-out and workable strategy for fighting ISIS. He did spar with Texas senator Ted Cruz last night over the NSA bulk data correction program that just expired. Cruz supported ending that program. Well, Rubio says it was an important tool for investigators. And that continued on the campaign trail today.
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MARCO RUBIO: If, God forbid, today there is a terrorist attack on our homeland or anywhere in the world, the first thing everyone's going to want to know is, why didn't we know about this, and why were we not able to stop it? And the answer better not be because we took away a valuable tool in the toolbox.
CORNISH: Sarah, you're speaking to us from New Hampshire. You've been out there on the campaign trail. How visible has Rubio been, and with just six weeks left until the first nominating contest, what's he doing to improve his chances?
MCCAMMON: Well, arguably, he hasn't been that visible. I mean, he hasn't had the surge that some of his opponents have had, so he's making a big push. He actually started off this morning in Iowa, made his way here to New Hampshire. Then we're heading back to Iowa tonight, where he will be campaigning tomorrow, trying to break through in these critical early states. Rubio is often compared to Ted Cruz, who has had a surge in the polls. He jumped to first in Iowa in the venerable Des Moines register poll. And Rubio is spending the next several days campaigning in Iowa. And Cruz will be campaigning in states that have primaries on Super Tuesday in early March.
CORNISH: Speaking of Ted Cruz, there was a lot of hype going into the debate about a clash between him and Donald Trump, who's still leading in the polls. That didn't entirely play out in the debate - right? - that they more or less played nice with each other. But what about Cruz and some of the other candidates?
MCCAMMON: Well, you know, we did see that sparring between Rubio and Cruz. And I think on the campaign trail, we're seeing Rubio punching up at Cruz, who is getting some of those big endorsements and kind of gaining in Iowa. Rubio and Cruz do have similar resumes. You know, they're both senators from southern states with parents who immigrated from Cuba, but Cruz is unpopular in his own party, including among his colleagues in the Senate. So I think you see Rubio painting himself as a more sensible alternative.
But Rubio has to be careful how he does that. He can't afford to anger those very same voters he's trying to win over by insulting his opponents who are popular with them. And today, he said he likes everyone on the Republican side, but Rubio stresses there are differences.
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RUBIO: It's easy to stand up and say I will destroy ISIS; I will make the sands in the Middle East glow in the dark. Well, that's fine, but you have to have something to do that with.
MCCAMMON: So that's a reference to something else Cruz said recently. He said he'd carpet bomb ISIS. Now, Rubio today said you can't attack ISIS without a strong military, and he's criticizing military spending cuts which Cruz has supported.
CORNISH: Sarah, in the time we have left, what have you heard from voters in the aftermath of this debate?
MCCAMMON: You know, Audie, a few of the Republican voters I talked to today are worried about the tone of this campaign. I asked about the back and forth, and they said there's too much of that. They don't want to hear Republicans tearing each other down, and they're worried that infighting will weaken the party's eventual nominee and give a win to the Democrats.
CORNISH: That's NPR's Sarah McCammon on the campaign trail with Marco Rubio in New Hampshire. Sarah, thanks so much.
MCCAMMON: Thank you. Transcript provided by NPR, Copyright NPR.