Last night’s debate for the Republican presidential candidates didn’t produce quite as many memorable moments as the last one, but it was good to see Fox News’ Chris Wallace press Mitt Romney on one of the former governor’s most important weaknesses.

“Governor Romney, you have changed your position in the last 10 years on abortion, on gay rights, on guns. You say keeping an open mind is a strength, but some of your critics say that every one of these moves has been to your political advantage. When you were running in Massachusetts, you took liberal positions. Running now as president, you take more conservative positions. Is that principle or is it just politics?”

Romney took issue with the notion that he changed his position on gay rights, but explained that he reversed course on abortion after he “studied it in some depth.”

I’m still not sure who would find this persuasive. In 2005, when Romney abandoned his pro-choice position — he was an “unequivocal” supporter of abortion rights three years prior — Romney was 58 years old. He’d never really thought about the issue until, coincidentally, he started gearing up for a presidential campaign?

In any case, the pushback only allowed Wallace to clarify matters further.

“If I may, sir, in 1994, when you were running for the Senate, you wrote a letter to the Log Cabin Republicans in which you said, ‘I am more convinced than ever before that, as we seek full equality for America’s gay and lesbian citizens, I will provide more effective leadership than my opponent,’ who was Ted Kennedy.

“In 1994, you also said you supported not only an assault weapons ban, but also a five-day waiting period. And in 2002, when you were running as governor, you said that you supported the tough gun control laws in Massachusetts. And then as you say in 2004, you also signed an assault weapons ban.”

This left Romney a little flummoxed, and struggling a bit to explain why he opposes discrimination, except when it comes to discriminating in marriage laws.

As Benjy Sarlin noted, “The exchange was a good reminder that, for all the talk about Romney’s flip flops, he hasn’t had to face too many tough, extended exchanges over them.”

That the tough, extended exchange had to come from a debate moderator, and not a debate rival, suggests the Republican field is missing an opportunity.

On a related note, on Wednesday, Romney told Sean Hannity that there’s nothing wrong with flip-flopping: “If you don’t learn from experience, if you don’t learn when you’re wrong then you are stubborn and stupid. So of course, over that period of time, there have been items where I would have changed their mind.”

For those keeping score, Romney argued in September that he doesn’t flip-flop, arguing, “I stand by my positions.” Soon after, Romney acknowledged that he does flip-flop, but that’s a positive trait: “In the private sector, if you don’t change your view when the facts change, well you’ll get fired for being stubborn and stupid.”

In November, Romney went back to his original position, insisting, “I’ve been as consistent as human beings can be.” And in December, Romney is back to acknowledging his inconsistencies.

Is there anything more meta than someone who flip-flops over flip-flops?

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.