Stapleton, a financial adviser, finished second last year in the seven-candidate Republican primary for governor. In 2012, Republicans lost both the governor’s race and the party’s challenge to Democratic Sen. Jon Tester, disappointments for the GOP in a state the party carried handily at the presidential level.
Baucus, 71, is one of six Democrats in the Senate seeking re-election in a state the president lost. Still, Tester held off a strong challenge from then-Rep. Denny Rehberg last year, and Baucus was sitting on a $3.6 million war chest as he began the 2014 cycle.
Stapleton is a Naval Academy graduate and served two terms in the state Senate, including stints as minority leader and chairman of the Legislative Campaign Committee.