Rep. Jeff Flake’s Senate campaign got a boost Monday afternoon from Sen. Jim DeMint, the influential South Carolina Republican and conservative kingmaker.

Sen. Jim DeMint (R-S.C.). (J. Scott Applewhite/Associated Press)

“When it comes to fighting wasteful Washington spending and parochial politics, nobody has done more to advance the cause of freedom than Jeff Flake. Nobody,” DeMint wrote.

“Jeff Flake has fought a lonely battle against earmarks for years, even when it meant standing up to members of his own party who refused to stop pork barrel spending,” he added. “Without his leadership, House Republicans would not have adopted the earmark moratorium last year.”

During his six terms in Congress, Flake has been known for parting ways from his party on issues, including earmarks and immigration reform. Once thought to be a shoo-in for the GOP nod to succeed Kyl, he now faces a primary challenge from Cardon, who is running to Flake’s right and is largely self-financing his bid. Former U.S. surgeon general Richard Carmona is running unopposed for the Democratic nod.

A Cardon spokeswoman did not immediately respond to a request for comment on the DeMint letter.

In a statement, Flake called the South Carolina Republican “one of the most recognized national conservative leaders and has been a reformer in the U.S. Senate.”

“I am grateful to have his support in this race and I look forward to joining his efforts in the Senate to support economic freedom and limited government,” he said.

Although the establishment vs. tea party proxy battle has played out in many races this cycle, what separates DeMint’s endorsement from that of some others is that the South Carolina Republican is known for investing significant resources in the candidates he backs.