Senator John McCain finally appeared on David Letterman's The Late Show on October 16, 2008, the day after the final presidential debate. A feud between David Letterman and John McCain erupted after the presidential candidate canceled his planned September 24 appearance at The Late Show. McCain, citing his need to return to Washington to deal with the economic crisis as his reason for the cancellation, instead appeared on Katie Couric's show, the CBS Evening News.NYT: Letterman: McCain's Cancellation Not Funny (September 24) LAT: McCain stands up David Letterman (September 25)

Letterman has spent several shows criticizing McCain's decision, including dedicating his September 25th "Top 10 List" to McCain's running mate, Sarah Palin.

• 10. Sometimes Sarah calls John McCain "Grandpa."
• 9. She stole that sexy librarian look from me.
• 8. Recently passed legislation to build a bridge to Funkytown.
• 7. Does great impressions of Tina Fey.
• 6. Favorite meal: moose nuggets and beaver jerky.
• 5. Working on Knight Rider spinoff about a talking snowmobile.
• 4. Favorite book? Late Show Fun Facts - available at fine stores everywhere.
• 3. Once spent a week in the hospital after attempting to put lipstick on a pit bull.
• 2. To improve her foreign policy experience, she recently went to the International House of Pancakes.
• 1. Only person I know who's not afraid to go hunting with Dick Cheney.

Republican presidential candidate John McCain appeared on The Late Show with David Letterman on April 1, 2008 and traded jabs with host David Letterman. McCain appeared at the end of Letterman's monologue that had begun with a joke mocking McCain's age: "He looks like the guy who goes in to town for turpentine."

McCain began his own monologue about Letterman with: "You think that stuff's pretty funny don't ya?" During an interview later in the show, the two discussed issues surrounding Iraqi casualties, the national credit crisis, and the U.S. prison at Guantanamo Bay, Cuba.