Ciresi, who once won a major settlement from the tobacco industry, made the announcement Monday weeks after he gave his campaign $2 million, the St. Paul (Minn.) Pioneer Press reported.

"Continuing the endorsement race would only lead to an unnecessary floor fight," the Mendota Heights lawyer said in a statement. "It is time to step aside."

Franken is now going head-to-head with University of St. Thomas professor Jack Nelson-Pallmeyer for the Democratic nomination. The winner will challenge Republican U.S. Sen. Norm Coleman' title='U.S. Sen. Norm Coleman' class='tpstyle'>U.S. Sen. Norm Coleman in the general election in November.

Ciresi gained statewide prominence when he represented the state in the case against tobacco companies in 1998 won a $6.1 billion settlement.

The lawsuit, which brought $440 million to Ciresi's Minneapolis firm, gained the release of 33 million pages of industry documents and pledges from the companies to restrict their marketing practices.