Although Letterman was known as McCain-friendly, so friendly in fact, that the senator announced his presidential candidacy on the “Late Show,” there is one mistake not to be made by any man who wants to get through to people and gain the sympathy of millions. No presidential candidate should ever drop out of Letterman’s show at the last minute and especially when there’s no better excuse than the “economical crisis.”

The “Late Show” host was so surprised by McCain’s cancellation of his scheduled appearance at the last minute, citing a need to go to Washington immediately, that he kept going on and on about it throughout the broadcast.

Republican presidential nominee John McCain dramatically announced on Wednesday that he will suspend his campaign to focus on the nation's financial crisis: "Tomorrow morning, I will suspend my campaign and return to Washington after speaking at the Clinton Global Initiative. I have spoken to Senator Obama and informed him of my decision and have asked him to join me."

His senior campaign adviser, Steve Schmidt, later told reporters that all appearances, rallies and TV advertising would be canceled, but things are still apparently unclear among McCain’s people. The Huffington Post, a left-leaning Web site, caught them on the wrong foot, as it claims to have called 15 McCain campaign offices in battleground states, and none said it was suspending operations, due to crisis or any other reason.

Letterman was so upset, that he kept mixing praises to the Arizona senator for his courage, recounting McCain’s years in a North Vietnamese prison camp and calling him “an honest-to-God hero,” with disappointed, yet cynical remarks on the “fishy” excuse for dropping out of the show. At the last minute, none the less. He repeatedly said that this wasn’t the McCain he knew and respected. “This doesn’t smell right,” Letterman continued. “Because this is not the way a tested hero behaves. I think someone's put something in his Metamucil.”

But disappointment reached its highest level, making room for sheer fury, masked under a comedic monologue, when Letterman got a hold of a live transmission in the CBS Evening News studio, where the Republican candidate was being prepared for airing, while the makeup artist was putting on a coat of foundation on his face.

Turns out, David had all the rights to feel upset and lied to, as McCain was at that very moment just a few blocks away and not rushing back to D.C. in an attempt to rescue the exploding economy. “He doesn’t seem to be racing to the airport, does he? Hey, John, I got a question! You need a ride to the airport?” Letterman said, while grinding his teeth.

After he was a “Late Night” guest for 12 times over the years, McCain took one wrong step that he might regret, as Letterman is one of the nation’s most influential hosts and influence is what one would need when running for president.

And Letterman is not one to forgive and forget that easily, for his famous quarrels sometimes last for a very long time, like the one of 16 years’ duration with Oprah Winfrey and another with rival late-night host Jay Leno.