Can Joe Biden get any dumber? Just last Thursday, the vice president said he didn’t blame the 41% of West Virginia Democrats who voted for an incarcerated felon over Barack Obama in the recent primary because they were acting out of frustration. Just before that, as the president put it, ol’ Joe had “got out a little over his skis” by coming out for same-sex marriage while his boss was still evolving.

On Tuesday Mr. Biden takes his act to New Hampshire, where he will speak at a campaign rally at Keene State College. One thing’s for certain: Anything remotely colorful will generate yet another round of news stories about the “gaffe-prone vice president.” Then again, in some ways that’s become Mr. Biden’s role.

In a recent documentary on Johnny Carson, Ed McMahon summed up his role as sidekick this way: “You had to be good, but not too good.” Every vice president faces that challenge. In Mr. Biden’s case, however, his reputation as resident bonehead brings at least one benefit: It distracts folks from asking whether the administration’s record really shows Mr. Obama as brilliant and nuanced as we are constantly told he is.