Forget John McCain's face-to-face encounters with Barack Obama, which wrap up Wednesday with their third and final debate. Thursday evening is when we'll find out just how thick McCain's skin is.

That's when he settles into the guest chair next to the TV star who has become his new, unrelenting nemesis -- David Letterman. Chances are they'll play nice. But given the grief Letterman has been directing McCain's way, the candidate surely will be entertaining less-than-friendly thoughts.

Promulgating a feud -- whether real or not -- is a tried-and-true technique for attracting attention on the talk show circuit. One of the founding fathers of late-night television, Jack Paar (at right), was a master at it.

Letterman, whose comedic persona long has included a crusty edge, embraced the role of spurned host after McCain canceled a scheduled "Late Show" appearance last month because of plans to hurry back to Washington -- but then remained in New York that night. Since then, Letterman monologues have been littered with barbs aimed at McCain.

And that continued to be the case tonight, despite the the Republican's effort to make amends and show up on the "Late Night" set Thursday. The Times' Matea Gold passes along, courtesy of CBS, some of Letterman's latest lines:

You heard what happened at a rally yesterday. Sarah Palin mistook some of her supporters for hecklers. And you know, confusion happens in all walks of life. For example, a few weeks ago, John McCain mistook her for a legitimate candidate. ... And tomorrow night is the final presidential debate. John McCain and Barack Obama. And John McCain is going to take this opportunity to unveil his new campaign persona. His new campaign personality, to really energize the last couple of weeks of the campaign -- Fighting Underdog. Fighting Underdog. ... And if that doesn’t work, then he’s going to go to Corrupt Bordertown Sheriff. And if that doesn’t work, Seen-it-All Bartender. And then Priest Who Tries to Communicate with Martians. And then the Alcoholic Safecracker. And then the Maniacal Hunter Who’s After Human Prey. And then the Shifty Racetrack Vet. And then the Retired Jewel Thief. And then the Archaeologist Who Scoffs at the Mummy’s Curse. ... I’ll say one thing about John McCain -- the guy is an optimist. He sees the glass as half full -- of his teeth.

And we'll say one thing about Letterman: He's more than doing his part to maintain the disparity a study identified in the political targets of late-night jests.

-- Don Frederick

Photo credit: NBC