It’s one thing when Sen. John McCain cancels an appearance on Letterman because of a financial emergency.

But then, like a cheating significant other, he’s caught being interviewed (live) by Katie Couric for the CBS Evening News.

Letterman wasn’t happy about this. He was never a fan of Sarah Palin, but he loves McCain (he loves Obama a little more, however).

This nine-minute video is worth the watch…

Just a year and a half ago, this was the scene — McCain announcing his bid for presidency on the same show…