David Letterman made it no secret how he feels about John McCain's cancellation Wednesday of a scheduled appearance on the funnyman's "Late Show" on CBS -- devoting his monologue to vent about the cancellation and mentioning it with disapproval throughout the show.

"I'm more than a little disappointed by this behavior," Letterman said. "We're suspending the campaign. Suspending it because there's an economic crisis, or because the poll numbers are sliding?"

Letterman's "Top 10" centered on what questions people would ask the McCain presidential campaign, and the talk-show host even talked about the cancellation with guest Keith Olbermann.

As the show went on, more drama unfolded during the taping of the "Late Show."

Earlier, Letterman revealed to the audience that McCain personally called him to apologize for the cancellation because the presidential candidate was in a rush to the airport.

But later in the show, Letterman was informed that the GOP candidate was a mere five blocks away getting set up for an interview with CBS News' Katie Couric. The funnyman even showed a live feed of the candidate in real time -- not on his way to the airport!

True to form, Letterman managed to weave in lots of jokes about the cancellation.

"Maybe if he hadn't taken two years off to run for president, he wouldn't have to rush to Washington now to deal with the crisis," Letterman said.

He went on to say this about McCain's campaign:

"But when you call up, and you call up at the last minute and you cancel a show -- ladies and gentleman -- that's starting to smell…," Letterman said. "It makes me think something is going haywire with the campaign."

A seemingly frustrated Letterman then questioned why McCain's VP running mate, Sarah Palin, didn't fill in for McCain, asking, "Where's your second-string quarterback?"