Jon Tester

Jonathan "Jon" Tester (born August 21, 1956) is the senior United States Senator from Montana, serving since 2007. He is a member of the Democratic Party.
Tester was first elected to the Senate in 2006, beating Republican incumbent Conrad Burns in one of the closest Senate races of that year. He won re-election in 2012 against Rep. Denny Rehberg in another close race. 
Tester previously served as the president of the Montana Senate and worked as a music teacher and farmer. He became the senior Senator in 2014 when Max Baucus resigned to become U.S. ambassador to China. He is currently the dean of the Montana congressional delegation.