A look at Letterman's top 10 political moments

David Letterman's most memorable 'Late Show' moments
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David Letterman's most memorable 'Late Show' moments 01:36

Washington (CNN)David Letterman's "Late Show" ends Wednesday night, but his "Top Ten" segment at times shaped the late-night political conversation. In honor of his last show, here are the top ten political moments on his show.

1. After skewering Sarah Palin's teenage daughter on a prior program, Letterman was forced to apologize for some parts of his routine. The comedian joked that Yankees baseball player Alex Rodriguez had "knocked up" the daughter.
Letterman acknowledged that that joke was "borderline" but said he pursued it "in an act of desperation to get cheap laughs, which is what I've been doing for the last 30 years."
"I would never, never make jokes about raping or having sex of any description with a 14-year-old girl," Letterman said, noting that he was referring to her 18-year-old daughter, not the 14-year-old one. "I would never, never think that it was funny to use a 14-year-old girl as a joke like this, for God's sake."
    2. Letterman also attacked Palin's running-mate, John McCain, after he bailed on a 2008 appearance when he temporarily suspended his campaign. Letterman was clearly offended.
    "When you call up at the last minute and cancel a show, ladies and gentlemen that's starting to smell. This is not the John McCain I know," Letterman said, criticizing him for quitting the campaign during the final months. "This is not the way a tested hero behaves."
    The jokester encouraged McCain to allow Palin, his "second-string quarterback" to campaign in his stead rather than unilaterally suspending operations.
    3. Letterman began his first show right after the Sept. 11, 2001 attacks with a somber monologue addressing the tragedy from New York City.
    "We've lost 5,000 fellow New Yorkers, and you can feel it. You can feel it, you can see it," Letterman said as he began his speech, praising Mayor Rudy Giuliani's response to the attacks. "Rudolph Giuliani is the personification of courage."
    4. Letterman hosted his show during the entire presidency of George W. Bush, a president whose verbal miscues provided fodder for all late-night hosts.
    To commemorate the end of Bush's presidency, Letterman aired nearly four straight minutes of Bush mistakes in a recurring segment titled: "Great Moments in Presidential Speeches."
    "We have to unload what was a tremendous, rich heavy laden vein of comedy for us, like mining a dense vein of coal," he said.
    5. In one of President Barack Obama's visits on the "Late Show," the President and the comedian discussed surging racial tensions and whether any antipathy toward him was rooted in race.
    "First of all, it's important to realize that I was actually black before the election," the President deadpanned.
    "How long have you been a black man?" Letterman asked.
    6. Only a week after being impeached as Illinois governor, Rod Blagojevich decided to appear on Letterman's show.
    "Why exactly are you here? Honest to God," Letterman said before Blagojevich had even settled into his chair.
    "I've been wanting to be on your show in the worst way for the longest time," Blagojevich said.
    "Well, you're on in the worst way, believe me," Letterman retorted.
    7. Letterman had trouble hiding his skepticism for 2012 presidential candidate Herman Cain's tax plan, dubbed "9-9-9", routinely dismissing his vague answers and platitudes.
    Cain, at that time a promising Republican hopeful, faced a harsh comedian who grilled him on his platform. Cain accused Letterman of trying to talk him out of his plan.
    "I like it, it's clever. 9-9-9. It's fun," Letterman said. "You ought to get some sort of toll-free number. You dial 9-9-9, you get a free pizza."
    8. Letterman also recently had a tense exchange with Fox News host Bill O'Reilly, accusing him of making fake claims just like NBC newsman Brian Williams.
    O'Reilly said the situations weren't the same and that he had never fibbed on air.
    "We had a controversy, and we put forth what my side was, and they put forth what their side was, and folks decided. And it worked out okay for me -- I got even more viewers."
    9. Soon after the "Late Show" debuted on CBS, Letterman hosted Vice President Al Gore. Letterman ribbed Gore for his reputation as a boring, excitement-free politician who rarely landed or tried his own jokes.
    Gore said he didn't mind that caricature or Letterman's jokes -- and even offered his own.
    "How can you tell Al Gore from a room full of Secret Service agents?" Gore asked. "He's the stiff one."
    10. When interviewing fellow funnyman Al Franken, now a senator from Minnesota, Franken encouraged Letterman to think about what he should do after he left the "Late Show."
    Letterman asked what he could do to improve Indiana politics -- and Franken noted there would be an open Senate seat in the Hoosier State.
    "I think you should run," Franken told him.