When Newt Gingrich called CNN anchor John King’s decision “despicable” to begin last Thursday’s GOP debate with a question about Gingrich’s second wife, the Charleston audience responded with a standing ovation. Surely, I thought to myself, South Carolina Republicans are not going to vote for a candidate just because he is good at dressing down the media.

Then I saw a TV ad that used a squealing pig to sell car insurance, and I realized that people don’t always make the most carefully considered choices. It prepared me for the Gingrich landslide victory Saturday.

Exit polls indicate that electability was the most important factor behind the Palmetto State vote; 51 percent of those who care most about picking a nominee who can beat Barack Obama voted for Gingrich.

These folks clearly are unaware of the Fox News poll that found that only 27 percent of voters have a favorable view of Gingrich, whereas 56 percent don’t like him.

Many Gingrich supporters have assured me that the former speaker of the House was the best Republican because he would trounce President Obama in the debates. Claremont McKenna College professor of government Jack Pitney, however, points out: “Gingrich knows how to make Republicans applaud. That’s very different than appealing to a broad electorate.”

Pitney does not see Gingrich as the most electable Republican. For one thing, Pitney noted, “people who aren’t Republicans don’t like him.” Pitney remembers 1996, when Gingrich was such a polarizing figure that President Bill Clinton ran ads against GOP presidential nominee Bob Dole and Gingrich — as if Gingrich, not Jack Kemp, were Dole’s running mate.

We all have met guys like Gingrich before. At first, they seem charming and authentic, but over time, you watch them burn everyone around them.

Gingrich had so much promise when he became speaker in 1995, but he couldn’t ditch his supersize ego. He publicly whined about Clinton’s snubbing him on Air Force One. In his never-ending self-aggrandizement, Gingrich earned himself the first and only reprimand of a House speaker, as well as a $300,000 fine. When Republicans lost so many seats that they decided to oust Gingrich in 1998, he accused them of “cannibalism.”

A Clinton aide told The Washington Post that the White House was in mourning, as “Gingrich literally was the best thing the Democratic Party … had going for it.”

Voters have seen the same man on the 2012 trail. One week Gingrich is indignant about negative campaigning. The next week he is slinging mud.

One day he says he wants politicians who enabled Fannie Mae and Freddie Mac in jail; the next he boasts that Freddie paid him — some $1.6 million, it turns out — for his deep thoughts as a historian.

When it serves his purpose to berate King for asking a question about his second marriage, Gingrich gamely takes on the task. The rest of the time, he dispatches his daughters to explain his extramarital activities.

In the end, I believe that Republican primary voters are too pragmatic to nominate such a flawed candidate. So I’ll go with Pitney, who explained, “In South Carolina, people were trying to send a message that they didn’t like the mainstream media, but if it starts to appear that Gingrich has an actual chance of winning the nomination, then it’s a different vote. People’s calculations will change.”

Debra J. Saunders is a San Francisco Chronicle columnist. Her email address is dsaunders@sfchronicle.com.