White House advisers may privately grumble about how Joe Biden backed the president into a corner on gay marriage. But as Obama probably realizes, he owes Biden a debt of gratitude.

By Michael Reynolds/EPA/Landov.

It doesn’t really matter whether the substance of what Joe Biden said last Sunday about gay marriage was so very different from what his boss, Barack Obama, had said about the subject in the past (and there’s good evidence that it was not). What matters is the way that Biden said he was “absolutely comfortable” with same-sex marriage, which made what Obama had said before—that his own views were “evolving”—look too cute by half.

Because “too cute” is the paramount thing that this president has always assured us that he is temperamentally, intellectually, and politically contemptuous of being. Biden’s simple, canine candor—like a dog shaking water off his fur, the better to make himself clear, and dry—induced the president to state his own views out loud.

“At a certain point, I’ve just concluded that for me personally it is important for me to go ahead and affirm that I think same-sex couples should be able to get married,” Obama told ABC’s Robin Roberts on Wednesday, in an interview arranged with haste but exquisite calculation. “I had hesitated on gay marriage in part because I thought civil unions would be sufficient,” Obama said, adding, “I was sensitive to the fact that for a lot of people, the word ‘marriage’ was something that invokes very powerful traditions and religious beliefs.”

The problem for Obama was that almost no one thought he had genuine moral or religious qualms with gay marriage. He has now proved the point.

For several days White House political advisers had been agitated by Biden’s comments, but Obama may actually owe a debt to Biden. Though it may have been a surprise to Obama that it was his own vice president who put this issue front and center in an all-too typical 21st-century media firestorm, it cannot have been a surprise that the question would come up in this election year, if only because measures to deal with the issue are on state ballots, pro and con, or pending in state legislatures. Any debate moderator worth his or her salt next fall would have put this question to Obama in the presence of Mitt Romney. So it may have been a relief to deal with it now.