HARRISBURG -- Frequent presidential candidate Ralph Nader is asking state Attorney General Tom Corbett to return at least $15,900 in campaign contributions he received from a Pittsburgh-based law firm that helped House Democrats coordinate a 2004 effort to have Mr. Nader thrown off the Pennsylvania ballot.

Those Democrats now are under investigation by Mr. Corbett's office for using state resources to have legislative aides work on the petition challenges on work time. Democrats wanted Mr. Nader off the ballot so he wouldn't take votes from John Kerry, who was running as a Democrat.

Mr. Nader was removed over invalid petition signatures.

Evidence in the ongoing investigation, which has become known as bonusgate, indicates that the law firm Reed Smith LLP assisted in the effort.

Campaign finance reports show that the firm and its attorneys contributed at least $15,900 to Mr. Corbett's campaign in August 2008, a month after Mr. Corbett filed criminal charges against 12 House Democrats in the bonusgate investigation.

Mr. Corbett could not immediately be reached for comment this morning.

Mr. Nader's attorney, Oliver Hall, said that Mr. Corbett told him Friday that he did not intend to return the contributions.