South Carolina Sen. Jim DeMint today endorsed Rep. Jeff Flake in the Arizona GOP Senate primary.

In a letter to his Senate Conservatives Fund, a political action committee dedicated to electing conservatives to the Senate, DeMint wrote that “nobody has done more to advance the cause of freedom than Jeff Flake.”

Flake’s primary opponent is wealthy real estate investor Wil Cardon, who has put $4.2 million of his own money into his campaign and has made this a primary race to watch. They are running for the nomination to succeed retiring Sen. Jon Kyl (R), and the winner will take on former U.S. Surgeon General Richard Carmona (D) in the general election.

“We’ve always thought Jeff Flake was an outstanding candidate, but he didn’t need our help … until now,” DeMint wrote before requesting donations to Flake. “Flake is locked in a heated primary battle with Wil Cardon, a multimillionaire who has told reporters that he ‘won’t be outspent’ in this election.”