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Ken Buck Drops Out Of Senate Race, Runs For House Seat Instead

AP Photo / Brennan Linsley

The exchange means Gardner is more likely to coast to the GOP nomination to run against Sen. Mark Udall (D-CO).

Still, powerful conservative outside groups don't seem to be rallying behind Gardner. The Tea Party Express doubled down on its support for state Sen. Owen Hill (R), another candidate in the Senate race, on Wednesday night. Colorado state Rep. Amy Stephens (R) is also running in the GOP primary.

"It is evident that the D.C. Republican establishment is worried about the insurgent campaign of conservative Owen Hill and think that their hand-picked candidate will have better luck in defeating the Tea Party," an email from the Tea Party Express said on Wednesday. "Congressman Gardner has quickly become popular with the Washington, D.C. Republican establishment crowd and even joined the ranks of the Republican leadership last year."