You can often judge a politician's effectiveness by watching to see how well he performs when his back is against the wall. Newt Gingrich thrives on defense with a dark and demagogic brilliance. Mitt Romney wavers like a stalk of wheat in a summer storm.

And that stark contrast was the story of last night's Republican debate, potentially foreshadowing an upset win for Newt in the weekend South Carolina primary.

Not since Richard Nixon's heyday has a politician lashed out so theatrically at "the media," playing to the blood lust of the baying crowd, and trumping his own manifest flaws in the process. CNN host John King did Newt a big favor by launching the debate with this question: "As you know, your ex-wife gave an interview to ABC News and another interview with The Washington Post, and this story has now gone viral on the Internet. In it, she says that you came to her in 1999, at a time when you were having an affair. She says you asked her, sir, to enter into an open marriage. Would you like to take some time to respond to that?"

In theory, this should have been devastating for Newt, whose hypocrisy on conservative cultural values has long been notorious. Newt's second ex-wife, Marianne, said in the Post story that two days after he told her about his six-year affair with mistress Callista, he delivered a speech titled "The Demise of American Culture." As Marianne now laments, "How could he ask me for a divorce on Monday, and within 48 hours give a speech on family values?"

But Newt knew his audience last night. Yes, it's true that conservative South Carolinians hate amoral infidelity (at least when Bill Clinton does it), but they hate "the media" even more. Newt instinctively grasps the ethos of the ancient Chinese warrior Sun Tzu, who said, "Opportunities multiply as they are seized."

Hence Newt's seizure, his swift pivot from defense to offense: "I think the destructive, vicious, negative nature of much of the news media makes it harder to govern this country, harder to attract decent people to run for public office. And I am appalled that you would begin a presidential debate on a topic like that...."

And the crowd went wild. Fittingly, the North Charleston arena is officially known as a coliseum. Bathed in applause, Newt stood there with his imperious jutting jaw, like one of those Roman emperors who'd signal disdain for the wounded gladiators down in the pit.

King's question - which went to the issue of character - was legitimate. His mistake was that he asked it at the outset. Most viewers care far more about jobs and the economy, and Newt was right to observe that a sex story was the wrong way to "begin a presidential debate." But no doubt he was happy with King's choice, because the viewing audience for a debate is typically largest in the first 30 minutes. And reporters on tight deadlines were probably happy, because they knew immediately how to "lead" their stories, and they could spend the remaining time tweaking their descriptions of the confrontation.

Newt also claimed, amidst the cascade of applause, that Marianne's allegations were "false," but by that point nobody seemed to notice that he was publicly calling his second ex-wife a liar. South Carolina conservatives, who are supposedly so interested in judging a candidate's moral character, were instead distracted and mesmerized by the anti-media jihad - Newt's second this week. What better way to trump one's own heavy baggage, and perhaps win at the ballot box, than to beat up on Juan Williams and John King?

Now contrast Newt's performance with Mitt's.

Romney doesn't do defense nearly as well. Naturally, the key moment came when he was asked about his reluctance to release his tax returns.

King's question: "I want to ask you to go back in history a little bit. Back in 1967, your father (presidential candidate George Romney) set what was then a groundbreaking standard in American politics. He released his tax returns. He released them for not one year, but for 12 years. And when he did that, he said this: One year could be a fluke, perhaps done for show. When you release yours, will you follow your father's example?"

Mitt's initial response: "Maybe."

Now, imagine what Newt would've done with that question. Probably something like this: "I find it frankly appalling that the elite news media would bring my father into this discussion, not only because, as an historian, I can tell you that 1967 is fundamentally and transformatively different from 2012, but also because I am attempting to educate the elite media about big visions for the future, so I therefore resent the insinuation that my ideas should be ignored in favor of invading my family's privacy, and furthermore..."

Anyway, Romney rattled on, accompanied by his painfully skittish grin: "I - you know, I don't know how many years I'll release. I'll take a look at what the - the - what our documents are. (Jeers from the audience.) And I'll release multiple years. I don't know how many years. And - but I'll be happy to do that."

Romney's extreme wealth is his baggage, and he's clumsy when he tries to defend it. His wealth actually encumbers him. At one point in the debate, he described himself as "someone who has lived in the real streets of America," which made me wonder whether he was talking about his private driveway at the seaside manse in La Jolla, California.

South Carolina primary voters traditionally support the establishment Republican, and Romney will win tomorrow night if tradition holds. But Newt's visceral aggression - particularly when cornered - seems more in sync with the conservative mood this season (although Rick Santorum will eat into Newt's vote tally).

All told, tomorrow's likely voters would probably endorse this ancient observation from Sun Tzu: "The quality of decision is like the well-timed swoop of a falcon which enables it to strike and destroy its victim." Against all odds (yet again), Newt is in full swoop and flying high.

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I'll post here Sunday morning on the South Carolina results. On Monday afternoon, I'm scheduled for another Live Chat.

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