Jonah Goldberg shares with National Review Online readers his speculation about the reason for President Obama’s embrace this week of gay marriage:

There’s a “money primary” for incumbents, too, as evidenced by Obama’s unprecedented fundraising efforts. Indeed, according to data compiled by Brendan J. Doherty for his new book, The Rise of the President’s Permanent Campaign, Obama has had more reelection fundraising events than all the previous incumbent presidents since Richard Nixon — combined.

And that’s where the irony of Obama’s entirely disingenuous about-face on gay marriage really kicks in. Oh, I don’t think Obama is disingenuous about his support for gay marriage; if anything, he supports it far more than he admitted to ABC News. I think he’s disingenuous about its being an about-face.

Obama had to admit he was in favor of gay marriage because he was, in effect, forced to by an unexpected money-primary opponent: Joe Biden. Biden’s off-message support for gay marriage on Meet the Press made the figurative Democratic primary seem almost literal for a second. Biden got to Obama’s left, and it was killing the president with the segment of his base that matters most to him right now: super-rich liberal donors. These donors care about gay marriage a lot, and not just because roughly one out of six of Obama’s biggest bundlers are openly gay, according to the Washington Post.

Obama’s fundraiser at George Clooney’s house promised to be a tense and less than lucrative affair if he continued to let his vice president make him look like a politically vacillating wimp or a bigot in the eyes of his supporters. And so he ’fessed up to supporting gay marriage. His claim that he considers it a states’-rights issue is surely hogwash. (If he believed that, his administration would still be defending the Defense of Marriage Act.) But he said the words, which is all he needs to get the money spigots turned back on.

The question now is whether he moved too far left in the virtual Democratic primary to get back to the center in the real general election.