DENVER -

Former Republican state senator Mike Kopp kicked off his bid Tuesday to challenge Democratic Gov. John Hickenlooper next year with appearances at Red Rocks Amphitheater, Fort Collins, Colorado Springs and Pueblo.

Kopp, a Jefferson County Republican, is the fourth Republican to run against Hickenlooper, who is seeking re-election.
    
Kopp served in the state Senate from 2007 to 2011. He resigned his office after his wife died following a long battle with cancer. Kopp now works for Intermountain Rural Electric Association.
    
Kopp is a former Army Ranger who served in the Gulf War and a former "hotshot" firefighter before entering the state senate. He joins Secretary of State Scott Gessler, state Sen. Greg Brophy and former U.S. Rep. Tom Tancredo in the Republican race.