A mysterious advocacy group is targeting Republican frontrunner Donald J. Trump in a new online attack ad, the Washington Free Beacon has learned exclusively.

The ad, produced by the outside spending group Golf Cart Veterans for Truth, takes aim at Trump over his alleged cheating habits on the golf course, as detailed in a recent Washington Post report.

Asked about the numerous accusations of cheating from former golfing partners during a press conference last week, Trump dismissed them as "absolutely false," telling reporters: "I win at golf, that I can tell you."

Little is known about the group funding the ad, but the attack could offer a blueprint for Republican candidates whose previous efforts to criticize Trump have fallen flat.

"I think it works because it hits Trump where he is most vulnerable," a GOP strategist told the Free Beacon. "He's totally wedded to his self-image as a hugely successful winning winner who always wins. Go after that, and you might knock him down a peg. When it comes to marriage, golf, whatever, real men don't cheat."

A representative for the anti-Trump group also forwarded the Free Beacon a copy of their logo, which they recently printed out at a neighborhood FedEx and plan to distribute on street corners outside Trump courses worldwide.