Rep. Jeff Flake announced Monday morning he is running for the open Arizona Senate seat in 2012.

The six-term Republican had been eyeing the seat even before Sen. Jon Kyl (R) officially announced last week that he would retire at the end of his term. Flake is the first candidate to throw his hat in the ring, and gives Republicans a top-tier candidate to replace Kyl on the ballot.

With Kyl retiring, Democrats have said they plan to actively challenge for the seat. Roll Call Politics this weekend moved the race rating from Safe Republican to Leans Republican.

The political action committee of the anti-tax group Club for Growth immediately endorsed Flake’s candidacy. Club President Chris Chocola touted Flake as a “tireless champion for economic freedom” and his record of fighting earmarks.

“What’s really impressive about Jeff is that he had the guts to strongly oppose the worst policies of the Bush administration and of the previous Republican Congress, like earmarks, bailouts and the prescription drug entitlement,” Chocola said. “That’s the kind of courage in the fight for freedom and limited government we need in the U.S. Senate.”

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