CHARLESTON, S.C. — Former South Carolina Sen. Jim DeMint has maintained deliberate separation from the fray during the Republican primary here, but his voice entered the race in the final stretch this week.

In a radio ad released Thursday by the pro-Ted Cruz super PAC Keep the Promise, DeMint describes the Texas senator as “one of the most principled and courageous people I’ve ever worked with.”

“Anyone who says Ted Cruz is not likeable just doesn’t know him,” DeMint continues. “He’s fought hard and stood up against the establishment, and people don’t like that. I know that people in Washington didn’t like me either, and anyone who’s liked in Washington is probably part of the problem, so that’s a badge of courage as far as I’m concerned.”

The ad might easily be mistaken for an outright endorsement, but it is not. Rather, the audio was excerpted from a radio interview in which DeMint praised both Marco Rubio and Cruz, saying, “I’m proud of both of those guys.” He couldn’t endorse either of them, DeMint explained, because of his role as president of the conservative Heritage Foundation.

As a roster of former and current South Carolina elected officials have lined up to offer their endorsements in this pivotal primary, DeMint has been a notable and weighty exception. Not only is his opinion something of a lighthouse among many conservative Republicans, but he is also a longtime ally of Rubio and Cruz.

And therein lies the rub. They are each DeMint’s “political godchildren,” as Rep. Mick Mulvaney said recently.

The two presidential candidates forged their relationships with DeMint in nearly the same way. DeMint endorsed Cruz and Rubio while each was enmeshed in a heated Senate primary, each as the underdog against a better-funded opponent.

Rubio recounted DeMint’s role in his 2010 Senate race in his book “An American Son.” “Jim DeMint continues to be a source of sound advice and an inspiration to me,” Rubio wrote. He also lists DeMint in the book’s acknowledgements.

Cruz also recalled DeMint’s support in his own book, “A Time for Truth,” characterizing the former senator’s endorsement in Cruz’s Senate primary as “the most impactful.”

In the upper chamber, Cruz and Rubio have showcased dueling sides of DeMint’s own style: Rubio with his message of optimism and personal charm; and Cruz with his hunger for a fight. A former aide to DeMint reflected that an endorsement from DeMint might have been unnecessary or even counterproductive. The emergence of both Rubio and Cruz in this primary season reflects the success of DeMint’s mission to push the party to the right, regardless of which one ultimately prevails (if either one is able to win the nomination).

DeMint’s neutrality is more frustrating for the candidates themselves, however, as they look for any iota of momentum. So each camp has hinted that their candidate is really DeMint’s favorite son.

In a recent radio ad released by Rubio’s campaign, Rep. Trey Gowdy invokes DeMint in a back-and-forth with Sen. Tim Scott, who replaced DeMint in the Senate.

“You and I talk about it all the time,” Gowdy tells Scott in the ad. “Marco Rubio is the sixth most conservative member of Congress, House and Senate, according to Heritage, which of course is led by Jim DeMint right now.”

Voters who still put stock in DeMint’s views are left to reading tea leaves about his actual preference. Some of those signs point to Rubio, as key elements of DeMint’s old political network are supporting the Florida senator. Rubio’s campaign manager, Terry Sullivan, ran DeMint’s 2004 Senate campaign. Warren Tompkins, who leads Rubio’s super PAC, also worked on that race for DeMint. Luke Byars, who is also doing work for Rubio’s super PAC, was DeMint’s state director.

All the while, DeMint himself has been content to remain on the sidelines, allies say, as a new wave of Palmetto State elected officials have made their endorsements — many for Rubio or Cruz.

“I think he has been happy to see that mantle passed on to another generation,” said his former aide.