Will McCain make it to the 'Late Show'?

John McCain will face off with Barack Obama on television tonight, but he may face an even tougher opponent on Thursday.

The Republican presidential candidate will be on the "Late Show With David Letterman" (10:35 p.m., Ch. 2). Assuming, of course, McCain actually shows up.

As you may recall, three weeks ago McCain canceled an appearance on the show. And he did so at the last minute. And Letterman was visibly angry about it, launching into a blistering (and hilarious) attack on the Arizona senator.

It wasn't that the late-night host was unhappy that McCain canceled. Letterman told his viewers that the candidate had personally called him and said that he couldn't make it because he had to "rush back to Washington" to deal with the unfolding economic crisis.

Letterman was understanding. That is until he discovered that not only had McCain not left New York, but he was in a CBS studio across town doing an interview with Katie Couric.

And it wasn't like McCain did a quick interview and then immediately rushed back to the nation's capital. He spent the night in New York, gave a speech the following morning at the Clinton Global Initiative and only then returned to Washington.

I won't suggest for a moment that appearing on the "Late Show" was something vital. And when a McCain spokeswoman explained the following day that, in light of the Wall Street collapse, "this wasn't a night for comedy," she certainly had a point.

A point that McCain should have made when he called Letterman. Because what the candidate did tell a guy with his own TV show ended up sounding like "The dog ate my homework."

And if you've ever paid attention to Letterman's show, the not-a-night-for-comedy reasoning doesn't hold. This is the guy who was widely praised for his performance post-9/11. And Letterman has consistently done a better job of interviewing politicians than most broadcast journalists, for a couple of reasons.

First, he does take them seriously. Just days before McCain canceled, former President Bill Clinton was a guest. And while there were moments of humor, it was a serious discussion of people and issues.

And, second, Letterman asks tougher questions than most of the pseudo-journalists on the cable news channels. He tends to preface them with some variation of, "I'm just a dumb guy who doesn't really get it, but why" do they do or say the things they say.