Karl Rove went on Fox News last night to take on Vice President Biden, challenging Biden's assertion he had a private confrontation with President Bush in the Oval Office.

Rove, a deputy chief of staff in the Bush administration, said such an event never happened, and that Biden was rarely alone.

"I hate to say it, but he's a serial exaggerator," Rove said. "If I was being unkind, I'd say he's a liar."

Watch the political guru's remarks below: