Sen. Jim DeMint has endorsed Rand PaulRand PaulSunday shows preview: Trump sits down with Fox Trump stumps for Louisiana Senate candidate ahead of runoff Giuliani won't serve in Trump administration MORE in Kentucky’s Senate GOP primary race, putting him at odds with Senate Republican Leader Mitch McConnellMitch McConnellHeitkamp is Trump's top choice for Agriculture secretary: report Schumer calls for Senate probe into Russian interference Senate passes stopgap funding bill, averting shutdown MORE.

DeMint (R-S.C.) announced Wednesday he would support Paul, an eye surgeon who is the son of Rep. Ron Paul (R-Texas), through his Senate Conservatives Fund, which has raised hundreds of thousands of dollars for conservative candidate Marco RubioMarco RubioSenate clears water bill with Flint aid, drought relief What Trump's Cabinet picks reveal House passes water bill with Flint aid, drought relief MORE in Florida.

DeMint’s move will be seen by some Senate Republicans as a breach of protocol because he is stepping onto McConnell’s home turf to support a candidate McConnell does not.

McConnell on Tuesday formally endorsed Paul’s opponent, Kentucky Secretary of State Trey Grayson.

“I rarely endorse in primaries, but these are critical times,” McConnell said in a television ad for Grayson.

DeMint said in a statement that he's not trying to undermine McConnell.

"Senator McConnell and I are on different sides in this race, but I support him as our leader," DeMint said.

DeMint touted Paul as a strong advocate for balanced budgets, an opponent of Washington’s culture of spending earmarks and a supporter of term limits.

"I'm endorsing Rand Paul because he's a true conservative who will stand up to the Washington establishment," DeMint said. "Rand has been running on the issues that matter since the beginning of this campaign.

“He's not a career politician, and he's got the guts to stand up to the massive spending, bailouts, and debt that are being forced on us in Washington,” DeMint added.