DAVID GREENE, HOST:
With those stakes high in South Carolina, the political ads are getting more pointed.
As NPR's Brian Naylor reports, the candidates themselves are taking aim less at each other and more at the White House.
BRIAN NAYLOR, BYLINE: The day before the South Carolina primary, the remaining Republican candidates are making their final TV pitches to voters. Here's part of what the Mitt Romney campaign bills as its closing argument.
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MITT ROMNEY: President Obama wants to fundamentally transform America. I stand ready to lead us down a different path. This president has enacted job-killing regulations. I'll eliminate them. He lost our triple-A credit rating. I'll restore it. He passed ObamaCare. I'll repeal it.
NAYLOR: Newt Gingrich is also appealing to South Carolina Republicans by attacking President Obama, with a spot cut directly from his remarks at last Monday's debate.
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UNIDENTIFIED MAN #1: Only Newt Gingrich can beat Obama.
NEWT GINGRICH: More people have been put on food stamps by Barack Obama than any president in American history.
NAYLOR: These broadcast ads by the Gingrich and Romney campaigns are certainly tough on the president, but neither mentions the other Republicans in the race. But ads by the superPACs backing the candidates, which are not affiliated with the campaigns, are a different story.
For instance, here's a Web ad from the superPAC Winning Our Future, which supports Gingrich. It shows computer-animated characters staging a mock debate between Romney and the president.
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UNIDENTIFIED MAN #2: (As President Obama) Now, I agreed with Governor Romney on many things, but this presidential candidate Romney, I don't even know the guy. Then again, he doesn't seem to know himself.
UNIDENTIFIED MAN #3: Oh, come on. Governor Romney?
UNIDENTIFIED MAN #4: Winning Our Future is responsible for the content of this message.
NAYLOR: David Procter is director of the Institute for Civic Discourse and Democracy at Kansas State University. Procter says it's no accident that the Republican candidates themselves are hesitant to go directly after their GOP rivals.
DAVID PROCTER: What they're trying to do is to have themselves associated with positive messages. And then because of the rules of the superPAC, they are able to claim at least some level of deniability that they know anything about this.
NAYLOR: Another way of providing some distance, if not deniability if you're a candidate, is to use a surrogate to do the attacking. Here's a Web ad the Romney campaign unveiled this week, in which former Republican Congresswoman Susan Molinari talks about serving with then-Speaker Gingrich.
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SUSAN MOLINARI: Newt Gingrich had a leadership style that can only be described as leadership by chaos. The decisions that he would make today would be different decisions tomorrow, and a lot of the problems came from sort of the discipline that he lacked in order to get the job done.
NAYLOR: Whether it's surrogates or superPACs, University of Virginia Political Science Professor Paul Freedman says...
PAUL FREEDMAN: All else being equal, I would rather somebody else did my heavy lifting or did my dirty work when it comes to campaign advertising.
NAYLOR: Of course, Comedy Central host Stephen Colbert, with a mock superPAC supporting his mock candidacy, spoofs Gingrich and Romney in this Web video.
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UNIDENTIFIED MAN #5: Donate today, and we'll destroy both these guys and their superPACs with a merciless ad torrent so fierce, they'll wish they'd never been incorporated - an orgy of pure distortion leaving nothing behind but the clean campaign we all deserve.
NAYLOR: Now, some candidates do directly take on their opponents. Here's an ad from Rick Santorum.
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UNIDENTIFIED MAN #6: Obama's a liberal on social issues. Romney once bragged he's even more liberal than Ted Kennedy on social issues. Why would we ever vote for someone who's just like Obama?
NAYLOR: The University of Virginia's Freedman says just as most campaigns make a decision to distance themselves from direct attacks, it's also no accident that in the closing days of a race, the ads take on a sharper edge.
FREEDMAN: Campaign ads need to do two things. You need to solidify your base as you reach out to potential supporters of an opponent and give them reasons to vote against your opponent. And so as a race gets tighter, as it gets closer, as Election Day approaches, candidates at this point, you know, it's all in.
NAYLOR: And his advice for the beleaguered TV viewers in South Carolina who want to avoid these ads: Pick up a book.
Brian Naylor, NPR News.