Republican vice presidential nominee Paul Ryan has tapped former U.S. solicitor general Ted Olson to play the role of Vice President Biden in preparations for next month’s debate.

Olson is best known as the top Republican attorney who, along with New York attorney David Boies, led the legal battle against California’s Proposition 8, banning same-sex marriage. His first mock debate session with Ryan, a congressman from Wisconsin, came this past week.

Ryan spokesman Brendan Buck called Olson “one of the most skilled, intelligent and successful litigators in America — just the kind of opponent needed to prepare the congressman for Mr. Biden.”

“Joe Biden has been in elected office for more than 40 years,” Buck said in a statement. “There are few people in politics with more experience debating the issues than Joe Biden, so we are taking this process seriously.”

Olson has won three-quarters of the 58 cases he has argued before the Supreme Court, including the Bush v. Gore case that cemented George W. Bush’s 2000 presidential victory. Olson represented Bush in the case, while Boies represented Gore. For their work on the lawsuit, Time Magazine in 2010 named both men among its 100 most influential thinkers.

In addition to his 2001-2004 stint as solicitor general under Bush, Olson’s work in government includes his three years, from 1981-1984, as assistant attorney general for the Office of Legal Counsel under Ronald Reagan. He also has worked as private counsel for both presidents.

His selection gives Ryan a skilled debate partner with extensive Washington experience as he ramps up his preparations for the Oct. 11 faceoff at Centre College in Danville, Ky.

In a statement provided by the Romney campaign Saturday, former U.S. attorney general John Ashcroft praised Olson as a man who “possesses the extraordinary intellect, judgment and character to be a strategic asset in any endeavor.”

“Few lawyers have prevailed in as many of the country’s most challenging battles to protect our national interest as Ted has,” said Ashcroft, who served under Bush with Olson. “I, along with many other conservatives, welcome his increased participation in the Romney campaign.”

Rep. Chris Van Hollen (D-Md.), Ryan’s Democratic counterpart on the House Budget Committee, is playing the role of Ryan in Biden’s debate prep. Hollen and Ryan were spotted briefly exchanging words on the House floor Thursday, when Ryan made his first visit to the Capitol since being tapped to serve as Romney’s running mate.