Jonathan Martin catches this from an interview McCain did with Fox News, to be aired later:

"I'm not driven by Sen. Obama's schedule, but it's a very tough thing to do," McCain told Fox News's Carl Cameron in an interview to air tonight. "I'm working hard at it."

This is probably something McCain has to say, but the reality is that it would be better for McCain to wait to see whom Obama chooses. That's politics, and it would be foolish if the campaign didn't have a few candidates in mind depending on Obama's choice.

Still, McCain might surprise us with a preemptive announcement.