Yes, I confined Biden's competition to the male sex only because specimens like Boxer are off the charts and skew the sample too radically. One reason I give Biden the edge over his colleagues is his colossal vanity. He truly believes he's the smartest guy in the room, which gives his stupidity an especially high admixture of smug fatuity that puts it in a class by itself.
You know, you're right, the fact that he's thinks he's so smart is what makes him so funny. It's like he's the only one in the room who doesn't know he's a fool.
He's sort of the twenty-first's century Ted Baxter.