Bill Nelson was first elected to the U.S. Senate in 2000. A lifetime Floridian, he previously served six years as a member of the state Cabinet and 12 years as a congressman. Nelson is an expert on NASA who, after intensive training, spent six days on the Space Shuttle Columbia as a payload specialist. Since, he's worked to protect the environment and been an advocate for space exploration. Nelson is a Democratic Deputy Whip and serves on the Armed Services, Budget and Foreign Relations committees.