Senator 'Jake' Garn - who flew on the 'Discovery' Space Shuttle in 1985 as a payload specialist - and was the first sitting member of Congress to enter space. (Senator Glenn flew again - on Discovery - in 1998), Senator Garn was a Republican who represented Utah.
Senator 'Bill' Nelson flew on 'Columbia' in 1986 - he has been a member of the House of Representatives (1979-91) and is now a Democrat Senator for Florida.
Before entering Congress, 'Jack' Schmitt was a scientist-astronaut, and walked on the moon. He was the last but one person to do so. He served as a Republican Senator for New Mexico in 1977-83.