Story highlights Todd Graham: Rick Santorum had the best night of any of the debaters in any of debates

In last place in polls, with no one attacking him, he laid into opponents, Graham says

Calling Gingrich "loose cannon," Santorum hit him on issues, tenure as speaker, he says

Graham: Question on Gingrich marriage a mistake, gave Gingrich a chance to slam media

If I were a conservative Republican in South Carolina and Thursday night's debate was the first I'd watched during this primary season, the choice would be easy. Rick Santorum. I know: It surprised me, too.

While he might have fewer overall followers than the other three candidates, Santorum nonetheless (or because of this) debated flawlessly. It was the single most impressive debate performance in this long series from any of the candidates.

Newt Gingrich also had his moments, pulling out whatever "go-to" trick in his arsenal the moment required. But on the issues, and for conservative Republican South Carolina voters, Santorum was the one running on all cylinders.

Here's why he did so well:

First, nobody was attacking him. He had a free roll. So in this case, it paid for Santorum to be last in the polls. He attacked Mitt Romney and Gingrich and was never put on his heels by his opponents. With no predators in sight, Santorum dominated the environment like an Asian carp.

Todd Graham

Second, his criticisms were focused and covered important conservative issues. He hammered away on health care at both Romney. (At one point Romney actually made the error of calling his own plan "Romneycare." Next thing you know he will accidentally call it "Obamneycare.") And then Santorum laid into Gingrich on individual mandates, which the former House speaker supported for 10 years.

More than once, Santorum drove home the notion that Gingrich is a loose cannon and Republicans can't afford that in a nominee. He flatly stated that Gingrich has "no discipline." Gingrich had suggested earlier that Santorum should drop out of the race. "These are not cogent thoughts," Santorum responded in the debate, reminding the audience that he is "2 and 0" against Gingrich in both Iowa and New Hampshire, and with much less money.

And Santorum provided the first debate attack of Gingrich's leadership as speaker of the House. "I served with him. I was there. I knew what the problems were going on in the House of Representatives, and Newt Gingrich was leading this."

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He roasted Gingrich by stating that conservatives threw him out of his speakership after four years. These were effective critiques because they were personalized. When Santorum spoke, he was believable.

Finally, Santorum did a good job presenting his own ideas -- zero taxes for manufacturing corporations, his anti-abortion stance -- and his closing remarks were right on the mark. In them, he talked about his electability over President Barack Obama. He went point by point describing his differences with Obama on health care and bailouts -- reminding the audience not so subtly that Romney and Gingrich supported the bailouts. Santorum concluded by saying he was the only Republican on stage ever to beat an incumbent Democrat.

This was a mistake. Gingrich's marriages may be a campaign issue, but there's a difference between a campaign issue and a debate issue. Some concepts simply can't play out well in a debating format.

When this question came roaring out of the gate, I knew two things. First, the other candidates wouldn't take the bait and talk about something so lurid. After all, this isn't a simple question of divorce or marriage or fidelity. This question sought details. Who wants to debate Gingrich on the question of open marriages? Romney with his family history of polygamy? ("Yeah, Newt. Let's debate open marriages for a while!" ) It's no wonder that Romney immediately said, "Lets get to the real issues."

And second, Gingrich was about to play King like a fiddle. What happened? Playing the victim better than that hot girl who trips over a rock and falls down in a horror movie, Gingrich was "appalled" and "astounded" by the "vicious" and "negative" question, calling it "trash" to open a presidential debate with it. Theatrics or not, it stopped King and anyone else from daring to bring it up again.

And in asking it, King unwittingly played right into Gingrich's hand. One tip for debaters also holds true with lawyers (and moderators). Never ask a question for which you don't already know the answer. King should have heeded that advice.