Former Alaska Gov. Sarah Palin has thrown her support behind Jeff Flake in the Arizona U.S. Senate race.

Flake announced the endorsement Monday, saying he's gratified to receive Palin's backing.

Palin says in a letter to Flake that he has been a consistent leader in curbing spending by the federal government. She says he isn't afraid to go against fellow members of the Republican Party, either.

Flake faces businessman Wil Cardon in the Aug. 28 primary for the Republican nomination for the Senate seat now held by Jon Kyl, a three-term senator who is retiring.

Cardon said Monday he's concerned with the endorsement of only one group: voters in Arizona.

Former U.S. surgeon general Richard Carmona, who is a Democrat, will face the winner of the GOP primary in the general election.