Obama is on Letterman tonight.

It’s not uncommon, at least in some Democratic circles, to ponder the possibilities of a joint presidential ticket of Hillary Rodham Clinton and Barack Obama. And in most conversations, the names are listed in precisely that order.

But when that question is raised on tonight’s Late Show with David Letterman, Senator Obama asks for a bit of clarity.

“That would be a powerful ticket,” Mr. Letterman says of the two senators. “Undeniably that would be a powerful ticket.”

Mr. Obama replies: “Which order are we talking about?”

Pretty good line...