Jon Huntsman’s exit from the presidential race leaves five Republican candidates taking the stage tonight for a Fox News debate, co-sponsored by the Wall Street Journal and the South Carolina GOP.

I will update this post later with highlights. I don’t expect Newt Gingrich, Ron Paul, Rick Perry or Rick Santorum to do any real damage to Mitt Romney. Any comments about this debate or the GOP primary campaign are welcome in this thread.

UPDATE: I missed part of the debate, but some thoughts are after the jump.

My impression is that Newt has helped himself by opposing further unemployment benefits extensions and by vigorously defending his atrocious “food stamp president” rhetoric. The crowd loved his jobs plan for kids. Big applause line:

I believe every American of every background has been endowed by their creator with the right to pursue happiness, and if that makes liberals unhappy I’m gonna continue to find ways to help poor people learn how to get a job, learn how to get a better job, and learn some day how to own the job.

I thought Ron Paul’s answer to the question about military budget cuts was very strong, but I doubt it will go over well with the South Carolina Republican voters. I love how he pointed out that he twice as much in campaign contributions from active-duty military personnel as all the other candidates combined. They don’t want us to be involved in all these foreign wars, and they want us to focus our defense spending on our own country.

Mitt Romney seems to be playing not to lose. I laughed when he promised to release his tax return around April (that is, after he’ll have locked up the nomination).

Romney’s answer on the indefinite military detention powers in the NDAA was pretty despicable. He’s confident that neither Obama nor he would abuse this power. Al Qaeda people should not have any rights, he says. But so many of the people we’ve detained have no connection to Al Qaeda.

Perry seems mostly irrelevant to the discussion. I felt a little sorry for him when he got a question about Turkey’s membership in NATO during the foreign policy section of the debate. Predictably, he got big applause when he bashed the Obama administration’s criticism of Marines who urinated on Taliban corpses. Sad.

From what I’ve seen, Santorum is giving the “right” answer a lot of the time, but he’s not firing up the crowd the way Newt is.

When the candidates were asked about Social Security reform, Gingrich defended an optional privatized system, and Santorum went after him for “fiscal insanity.” For once, Santorum is right about something.

Late in the debate, Romney and Gingrich mixed it up over misleading super-PAC ads. Nice pivot by Romney: wouldn’t it be nice if we could make the super-PACs disappear by letting people give as much as they want to political campaigns?

He’s glossing over the fact that even if we allowed unlimited political contributions, some would prefer to funnel money through PACs that can run hit pieces, leaving candidates to focus on positive messaging.

I missed the early debate segment in which Romney defended his work for Bain Capital. It sounds like he did well with the audience there. Romney struggles when he gets a question he hasn’t prepped for:

Juan Williams asked if he still hunts “varmints.” Romney bobbles – says he’s been moose hunting. No, make that elk. Something with four legs. “I’m not the great hunter,” Romney admits.