(CNN) - A late night move has cleared the path for Republican Rep. Cory Gardner of Colorado to challenge Democratic Sen. Mark Udall in this year's midterm election.
State Sen. Owen Hill Monday night announced he was dropping his bid for the GOP nomination in Colorado. In an email to supporters Hill said "Congressman Cory Gardner has the best chance of defeating Mark Udall in November and I pray that he does."
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Hill was supported by many tea party activists and recently won the endorsement of the Tea Party Express, a leading national tea party organization.
Gardner initially decided against running for the Senate last year, but he changed his mind and announced last month that he would launch a bid. After Gardner jumped in, two other candidates, Weld County District Attorney Ken Buck (the GOP's 2010 Senate nominee) and state Rep. Amy Stephens, ended their Senate campaigns.
Hill's move, first reported by Colorado Peak Politics, means Gardner is now considered the all-but-certain GOP nominee, and can concentrate his efforts on challenging Udall. In Gardner, who was first elected to the House in 2010, the GOP has the top tier candidate they were looking for to take on Udall, who Republicans consider vulnerable.
"I want to thank Sen. Hill for doing what he believed was necessary to help unite our Party and work together to defeat Mark Udall in November," said Colorado Republican Committee Chairman Ryan Call, in a statement.
Democrats hold a 55-45 majority in the Senate (53 Democrats and two independents who caucus with the party), but are defending 21 of the 36 seats up in November, with half of those Democratic-held seats in red or purple states, like Colorado.
The GOP had what many considered a divisive Senate primary in Colorado in 2010, but a party official in Washington says things were smoother this time around, due to moves by the National Republican Senatorial Committee.
The official told CNN that "the NRSC developed strong relationships with Owen Hill, Ken Buck, and Amy Stephens – all part of a strategy to be inclusive rather than exclusive in primaries, which helped this transition go smoothly as opposed to some previous, more contentious, instances in previous years."