Even though he spent the better part of two shows hammering Republican presidential candidate John McCain for a last-minute cancelation a few weeks ago, David Letterman has invited the Arizona senator back to his show -- and McCain has accepted.

McCain is scheduled to appear on Letterman's "Late Show" on Thursday -- as long as he doesn't bail out again.

McCain was scheduled to appear on Letterman's show on Sept. 24, but called the host at the last minute to say he needed to head to Washington to help move a $700 billion Wall Street rescue package through Congress.

Letterman during his program showed a video recording of McCain, who was instead being interviewed by CBS News anchor Katie Couric.

MSNBC's Keith Olbermann was called in as a last-minute replacement, and the two made jokes at McCain's expense for much of the evening.

At the time Letterman said he felt like a "patriot" to let McCain off his commitment to deal with the economy but "now I'm feeling like an ugly date."

A McCain spokeswoman said at the time that because of the economic crisis, the campaign "felt this wasn't a night for comedy."

The following night, Letterman again lit in to McCain.

Thursday's appearance, a day after his last debate with Democratic rival Barack Obama, will be McCain's 13th visit to the CBS program.

Obama appeared on the Letterman show on Sept. 11, in the middle of a flap over his remark about "lipstick on a pig."

It's a term politicians have used for years to describe dressing up old policies with a new look -- without changing the meaning of the policy. Vice President Dick Cheney used it to criticize Sen. John Kerry in 2004. Sen. John McCain used it to criticize Sen. Hillary Clinton in May. And Obama used it on Tuesday to criticize McCain's new campaign theme of "change."

"You can put lipstick on a pig," Obama said to an outbreak of laughter among an audience in Virginia. "It's still a pig. You can wrap an old fish in a piece of paper called change. It's still going to stink after eight years."

The McCain camp reacted by accusing Obama of directing the pig comment at their vice presidential nominee, Alaska Gov. Sarah Palin. They demanded an apology.

On Letterman, the two made light of the matter.

"Let me ask you a question here," Letterman said. "Have you ever actually put lipstick on a pig?"

"You know, the answer would be no. But I think it might be fun to try," Obama said.