Jay Clark Buckey, Jr., is an American physician and astronaut who flew aboard one space shuttle mission (STS-90) as a Payload Specialist, Buckey withdrew from the race when which former Governor, from New Hampshire, entered the race? 
Jay C. Buckey:  Buckey withdrew from the race when former Governor Jeanne Shaheen entered the race. Jeanne Shaheen: Cynthia Jeanne Shaheen (née Bowers; January 28, 1947) is the senior United States Senator from New Hampshire, since 2009.
Jeanne Shaheen