McCain jokes about rivals with comedian Jon Stewart

"You know, Ron Paul is still in the race," McCain joked Wednesday during a taping of Comedy Central's "The Daily Show with Jon Stewart."

McCain deadpanned about the marathon race between the Democrats: "I hate to watch it. It's terrible. My heart goes out to them."

During the taping, McCain pretended to walk off the set when Stewart pressed him on whether President Bush is more of a liability for him than the Rev. Jeremiah Wright is for Obama. Then McCain fiddled with his microphone and mouthed "technical difficulties" into the camera.

The all-but-certain Republican nominee did reveal a few tidbits. His Secret Service code name, he thinks, "is 'jerk,'" and his choice for a vice presidential running mate is Dwight Schrute, a character on the NBC sitcom, "The Office," played by Rainn Wilson.

Comedy aside, McCain used the opportunity to challenge Obama, who moved a step closer to claiming the Democratic nomination after Tuesday's primaries in Indiana and North Carolina. Stewart asked whether McCain really believed the Islamic terrorist group Hamas had endorsed Obama. McCain's campaign issued a fundraising letter after a Hamas adviser, Ahmed Yousef, said the group likes Obama.

"It's indicative of how some of our enemies view America," McCain said. "And I guarantee you, they're not going to endorse me."

Off camera, Obama's campaign said McCain should apologize for "repeating tired and divisive attacks about Barack Obama that he knows are flat-out untrue."