That would explain the brain damage.

Via Politico:

Vice President Joe Biden said Monday at a campaign stop that he was known around the White House as a glass half-full kind of guy.

“I know I’m always characterized in the press as the White House optimist. Like I’m the new guy in town. As my grandfather would say, like I’m the guy who fell off the turnip truck,” Biden told campaign volunteers a surprise stop at an Obama campaign field office in Roanoke, Va.

Biden, who was joined by Sen. Mark Warner (D-Va.) and Gov. Tim Kaine (D-Va.), said it was true — that nothing could shake his optimism in America.

“I am more optimistic, my word as a Biden, I am more optimistic about America’s chance in the world today than I have been my whole career,” Biden said.