Ted Olson, the lead attorney arguing that California's gay marriage ban, Proposition 8, is unconstitutional, is helping Wisconsin Rep. Paul Ryan prepare for an upcoming debate against Vice President Joe Biden.

“Joe Biden has been in elected office for more than 40 years,” Ryan spokesperson Brendan Buck said. “There are few people in politics with more experience debating the issues than Joe Biden, so we are taking this process seriously. Mr. Olson is one of the most skilled, intelligent and successful litigators in America – just the kind of opponent needed to prepare the congressman for Mr. Biden.”

The news, first reported by POLITICO.com, has drawn heavy criticism.

Jerame Davis, executive director of the National Stonewall Democrats, charged that Olson was contradicting himself by assisting Ryan, the GOP running mate of Mitt Romney. Romney supports a federal constitutional amendment which would ban gay marriage.

“After he spent as much time, money, and reputation on overturning Prop 8 as he has, it's shocking to learn that Ted Olson would lift a finger to help the Romney-Ryan ticket during debate prep,” Davis told gay weekly the Washington Blade. “I honestly never expected Olson to so blatantly contradict his own argument by supporting a ticket that would stand squarely in opposition to what he calls one of the most important cases of his career.”

Olson, a Republican, served as U.S. solicitor general under former President George W. Bush and represented Bush in the Supreme Court case Bush v. Gore.

BuzzFeed's Zeke Miller reported that Olson and Ryan had already held one session in the past week.