Former Ohio Congressman Rob Portman played the role of Barack Obama during John McCain’s debate preparation all fall and spoke with FOX tonight about the experience.

Portman previously took on the roles of Joe Lieberman, John Kerry, Al Gore and John Edwards to assist President Bush and VP Cheney with debate preps during the 2000 and 2004 cycles.

His most challenging assignment: Lieberman. Portman calls him “unpredictable and authentic.”

The easiest study: Obama and Edwards. He says they both stick to script.