Washington (CNN) - Colorado Rep. Cory Gardner, a Republican elected in 2010, has decided to run for Senate, two sources tell CNN.
The 39-year-old Gardner joins a crowded field of Republicans seeking the GOP nomination, and will be considered a serious contender for the nod. Among those in the race are Weld County District Attorney Ken Buck, state Sen. Owen Hill, and state Rep. Amy Stephens.
The winner of the June 24 GOP primary will face Sen. Mark Udall in November. Udall was elected in 2008.
Just last year Gardner stated he would not run for the Senate in 2014, but as the political landscape appeared to be getting better for Republicans he reconsidered, said one of the sources, who spoke on the condition of anonymity.
Republicans only need a net gain of six seats to win back control of the Senate chamber in November.
Leaving the floor of the House of Representatives Wednesday after a vote on a GOP-backed bill on the IRS, Gardner declined to answer reporters questions about whether he was running for the Senate.
The congressman tried to change the subject and continued a conversation on his cell phone. When pressed again by CNN whether he was running for the Senate, Gardner referred to the bill on the House floor, saying "I'm happy to talk about the vote."
A couple of hours after the news about Gardner broke, a Colorado Republican source told CNN that Buck would drop his Senate bid and instead run for Gardner's House seat.
CNN Senior Congressional Producer Deirdre Walsh contributed to this report