Jay Clark Buckey, Jr. (born June 6, 1956, in New York City) is an American physician and astronaut who flew aboard one space shuttle mission (STS-90) as a Payload Specialist. Buckey briefly ran for the Democratic nomination to challenge New Hampshire Senator John E. Sununu, a first term Republican, when he was up for re-election in 2008. Buckey withdrew from the race when former Governor Jeanne Shaheen entered the race.