DENVER (AP) Republican congressman Cory Gardner plans to challenge Colorado's Democratic Sen. Mark Udall in a dramatic, last-minute entry into the race.
The front-runner in the race against Udall, Weld County District Attorney Ken Buck, said in an interview Wednesday that he will drop out of that race and instead run for Gardner's open House seat.
Gardner's entry into the Senate race was first reported by the Denver Post.
Buck narrowly lost a challenge to Democratic Sen. Michael Bennet in 2010, and some Republicans have been concerned that the mistakes Buck made then would doom him against Udall.
Gardner is a well-regarded congressman viewed as his party's brightest star in the state. He was elected in the tea party wave of 2010 that helped hand Republicans control of the House.