Donald Trump’s ploy to grab attention away from Thursday night’s Republican presidential debate — and his enemies at Fox News — appears to be working. Two candidates invited to attend the undercard debate, former Arkansas Gov. Mike Huckabee and former U.S. Sen. Rick Santorum from Pennsylvania, have indicated that they will attend Trump's event in Des Moines, Iowa, that is billed as a fundraiser for a charity for veterans, according to a series of tweets.

The billionaire businessman's event has already sold out two days after he announced it, CNN reported Thursday afternoon.

Not all of the undercard participants are on board for Trump's event, however. The campaign of former Hewlett-Packard CEO Carly Fiorina offered to donate $2 million to veterans if Trump agreed to debate her, seemingly baiting the real estate mogul in a tweet Thursday that referenced the still-brewing animosity between Fox News anchor Megyn Kelly and Trump.

In fact, the main point of contention for Trump dropping out of the debate was Fox's refusal to drop Kelly as the debate's moderator, the Washington Post reported. Trump has clashed with Kelly before, with her asking him in the first Republican debate about some disparaging remarks he has made toward women.

Trump has since stated Kelly treats him unfairly, and has accused Fox News of using him to jack up their ratings. Trump has dominated the GOP race so far in the polls, and has dominated the national headlines as well.

Trump hasn’t specified what exact veterans groups would receive the funds from his rally. Huckabee said he wasn’t invited to the main debate, and that if nobody is going to watch him, he doesn’t feel the need to be at the undercard debate.

"It's to honor the troops, it's not an endorsement of Donald Trump's candidacy,” Huckabee said Thursday, according to the Hill. “I'm still running for president, we've got the caucuses Monday night, but I'm delighted to join with Donald Trump in an effort to salute the veterans.”