Rick Santorum has been angry for days over an ad from Mitt Romney's SuperPAC claiming Santorum supports letting criminals vote. Unfortunately, Santorum's position is a bit more nuanced than Romney claims, and if there's anything Republicans don't fully understand, it's nuance.

We begin with Juan Williams asking the question:

Senator Santorum, today you said Governor Romney is guilty of distorting your record as well as of "lies and hypocrisy". You said this behavior is classic Romney and no one's holding him accountable. So, the same question that Kelly asked, this time to you.

Should these barbed personal attacks against fellow Republicans be abandoned by the candidates?

This launched a snowball of -- you guessed it -- personal attacks. Personal attacks launched while claiming to be above the fray. Personally, I was gratified to see them take aim at Romney. Until now, they've avoided it at all costs and it's probably too late now to make any difference, but it's still something worth doing.

After the obligatory self-congratulations from Santorum, he lays out his objection to Romney's SuperPAC attack.

SANTORUM: Governor Romney's SuperPAC has put an ad out there suggesting that I voted to allow felons to be able to vote from prison because they said I allowed felons to vote and they put up a prisoner - uh, a person in a prison jumpsuit.

I would ask Governor Romney, do you believe people who are felons who have served their time, who have exhausted their parole and probation, should they be given the right to vote?

Romney then exercises his right as the frontrunner to filibuster, going on about how he doesn't know what his SuperPAC does, blah blah blah. Santorum interrupts, requesting an answer to his question. It was kind of a nice contentious moment, actually. The audience agreed. As an aside, the audience reaction at this debate was really weird. It was like watching a football game, or lions eating centurions or something.

This was also the first of many interludes where Mr. Romney let his arrogance hang out all over the stage. He was determined to be the frontrunner and to swagger around letting everyone know that, too. Honestly, Santorum's question was a good one, but Mr. Romney tried very hard to filibuster it to his advantage.

Santorum used the moment to pander a bit to the African-American community as he reminded Mr. Romney that this was a big deal to them, and it was, after all Martin Luther King day. There was also a lot of this kind of condescension all night. Between Newt telling black women they could marry their way out of poverty to Rick Perry just whistling Dixie all night long to his faithful dogs in the audience, it was laden with classic Republican patrician disdain for those who aren't white or fortunate. At any rate, Santorum pointed out that there are disproportionately high incarceration rates among African-Americans, particularly on drug charges. This is true, though he neglected to point out that the Obama administration has sought to find a balance on drug policy and incarceration rates.

Santorum clarifies further:

The bill I voted on was the Martin Luther King Voting Rights bill. And this was a provision that said, particularly targeted to Africans Americans [sic] and I voted to allow them to have their voting rights back once they completed their sentence. Do you agree with that?

To which Mitt Romney finally replies:

Yeah, I don't think people who have committed violent crimes should be allowed to vote again.

Note the qualifier. Jack Abramoff must have sighed a huge sigh of relief with that, given his own felony conviction and time served, parole served, and launch on the book tour shortly thereafter.

Santorum had laid a perfect trap, and Romney walked right into it. Straight in. With a smile, Santorum asked a follow-up question:

Very interesting you should say that," he said, "because in the state of Massachusetts when you were governor, the law was that not only could violent felons vote after they exhausted their sentences, but [they] could vote while they were on probation and parole, which was a more liberal position that I took when I voted for the bill in the Congress.

This was probably the only time in the entire debate I saw Romney really rattled, but Santorum did a great job knocking him off his rhythm, and most importantly, off his high horse. He managed to blame the Democrats in the Massachusetts legislature for that particular rule, but by then the damage was done. The ensuing back and forth did nothing to rehabilitate Romney, and ultimately Rick Santorum summarized exactly what had been said at the end of the exchange.

What the governor said is he didn't propose anything to change that law and what he's saying is that the ad that says that I said that I voted to allow felons to vote is inaccurate. And it is inaccurate, and if I had some SuperPAC that was supporting me that was inaccurate, I would go out and say "Stop it." That you're representing me and you're representing my campaign, just stop it.

Santorum's position is admirable, but I would be very surprised to discover that he ever suggested the SuperPACs who flogged the issue of Barack Obama's birth certificate or the Jeremiah Wright sermons as if Mr. Obama had written them himself should just "stop it." No, Santorum is all for civility between Republicans but not so much when running against Democrats. Have a look at some of his 2006 ads against Robert Casey.

At any rate, this round went to Mr. Santorum. Mitt Romney should consider being a little less overconfident about his nomination possibilities and a little bit more on the ball with regard to debate answers.