The Associated Press is reporting that GOP economist David R. Malpass will run against Gillibrand in next fall's election.
Malpass is a former adviser for 2008 presidential candidate Rudy Guliani. He also worked for former presidents Ronald Reagan and George H.W. Bush.
GOP pundits see Gillibrand as vulnerable because she was appointed to the post by an unpopular governor -- plus, her approval ratings really haven't budged since she took over for now-Secretary of State Hilary Clinton.
Former Governor George Pataki has been viewed as the strongest potential candidate, but he says he won't run.
Malpass faces primary challengers in former Long Island legislator Bruce Blakeman and former Westchester Congressman Joe DioGuardi.