Debate coaches advise against making personal -- ad hominem -- attacks. But there are two kinds of personal attacks, and Rick Santorum engaged in both of them in attacking Newt Gingrich at Thursday's debate slugfest. 

One kind of ad hominem attack focuses on the target's moral uprightness (or lack thereof) or his personality. Albeit obliquely, Santorum suggested that voters should pay attention to the complaint by Gingrich's ex-wife that he had once asked her for an open marriage.  Note especially the implication that it isn't enough that Gingrich got religion and asked God for forgiveness: 

 "I've answered this question repeatedly throughout the course of this campaign. I am a Christian too. And I thank God for forgiveness. But, you know, these -- these are issues of our lives and what we did in our lives. They are issues of character for people to consider. But the bottom line is those are -- those are things for everyone in this audience to look at. And they're going to look at me, look at what I've done in my private life and personal life, unfortunately." He obviously didn't mean "unfortunately." 

Less sensationally, but still in the realm of  the first sort of ad hominem attack, Santorum  accused Gingrich of grandiosity and hinted that the former speaker of the House was erratic if not actually unstable: "I don't want a nominee that I have to worry about [my]  going out and looking at the paper the next day and figuring out what is he -- worrying about what he's going to say next." Oh, that Newt! 

Sticklers for debate decorum would consider these attacks out of bounds. Maybe so. But Santorum also engaged in a different sort of ad hominem attack on Gingrich that was perfectly proper: a critique of his leadership skills: 

"Four years into his speakership, he was thrown out by the conservatives. It was a coup against him in three. I served with him. I was there. I knew what the problems were going on in the House of Representatives when Newt Gingrich was leading this -- leading there. It was an idea a minute, no discipline, no ability to be able to pull things together." 

The focus here is not on the issues, which are supposed to dominate debates.  Echoing Michael Dukakis, of all people, Santorum was emphasizing the importance of competence. It's ad hominem, but it's not a cheap shot. 

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--  Michael McGough

Photo: Rick Santorum participates in a Republican presidential candidate debate at the North Charleston Coliseum in S.C. on Jan. 19. Credit: David Goldman / AP Photo