Pals again? Well . . .

Republican nominee for president John McCain finally turned up at "The Late Show with David Letterman" id="PECLB004157">David Letterman" Thursday night, but by the third commercial break, he probably wished he hadn't.

The host was tough, and his subject resolutely remained on message. This encounter turned into an interview of the teeth-pulling variety - at times playful, but only rarely. For those of you who missed it, not to worry: The soundbites will be everywhere this morning.

Almost from the very moment McCain walked on stage at the Ed Sullivan Theater, David Letterman bluntly asked, "What exactly happened?"

"I screwed up," said the nominee, and laughed.

But after that point, the laughter - as the saying goes - pretty much stopped.

Letterman grilled McCain on the hunt for Osama Bin Laden, the financial crisis and especially his running mate, Sarah Palin" id="PEPLT0007504">Sarah Palin. McCain arrived with some pre-cooked lines - or ice-breakers - of his own, but those mostly hit the stage with a thud. Of Letterman's endless rants the last couple of weeks concerning his last-minute cancellation as a guest on "Late Show," McCain noted, "I haven't had so much fun since my last interrogation." Or, "Now is not the time to raise anybody's taxes, except yours, and when I'm president, I'll do it. Share the wealth, share the wealth."

Thursday night, in fact, was perhaps most notable for who was not there - Sarah Palin, McCain running mate and late-night-comic punching bag. Letterman had broadly hinted on Wednesday's program that she might actually turn up last night, but a guest appearance may be a long shot now. Letterman peppered McCain on her qualifications, experience and even campaign declarations (such as Barack Obama" id="PEPLT007408">Barack Obama's association with "terrorists," notably former Weather Underground" id="ORCIG000029">Weather Underground member William Ayers.) Said Letterman, "You will also admit you can't control a hundred percent" personal interactions with other people, then asked about McCain's relationship with convicted Watergate burglar and now radio host G.Gordon Liddy.

McCain noted that he was "not in any way embarrassed" by his association.

Letterman did secure a promise from McCain: "If you are elected . . . I'd like Sarah Palin here."

We'll see.