Last night, Herman Cain made a big splash when he backed into pro-choice language on abortion last night on CNN — apparently by accident — when he said he is personally fully against abortion but doesn’t think that the government should tell women what to do. This is already shaping up as a very big deal. Cain is leading in some polls, so other Republicans may use this slip up to try to take him down, and he’ll have to address it.

In other words, this could mean the end of Cain’s 15 minutes.

Republicans certainly would never nominate anyone who was actually pro-choice, and anti-abortion activists won’t forgive anyone who stumbled this badly on the issue, even if he walks it back back (as I expect he will) and clarifies that he misspoke himself and he’s actually 100% pro-life. So this is at the very least a severe blow to his campaign. Given that he’s not a serious candidate, it gives Republicans a clean shot at bashing him for long enough to finally remove him from the top of the polls. As such, it can be seen as a lucky break for Republicans who know that it’s really not a good idea to have a presidential candidate who can’t manage to put three sentences together on most topics without an embarrassing gaffe.

The truth is that Cain’s abortion screwup is really a distraction from the real question about abortion in the GOP race, which is whether social conservatives can live with Mitt Romney, who has flip-flopped on the issue over the years. So pay less attention to how Cain deals with this latest flap, and more to whether social conservatives start shifting solidly to a stop-Romney candidate. As Ed Kilgore notes in a good column today, time is starting to grow very short. Cain’s 15 minutes are indicative of a larger story here, which is that social conservatives can’t bring themselves to accept Romney. As Cain’s 15 minutes expire, it’s decision time for social conservatives. And few if any decisions will be as central to determining Obama’s opponent next year than this one.