When he puts his hand on the Bible and swears that he will uphold the constitution:

“There is — you could make a case that articles of impeachment might be appropriate. But ladies and gentlemen, politics is the art of the possible, not the constitutional.”
— Senate Judiciary Chairman Joe Biden (D-DE), quoted by The Hotline, on whether a case could be made for impeaching President Bush.

Definitely in the running for the “candidate mostly likely to keep his foot in his mouth the entire campaign” prize but he does have a strong contender in Newt.
Tags: Joe Biden, presidential candidate, Democrat, election, politics, impeachment, Bush