If the Republican Party continues to treat Donald Trump unfairly, the billionaire real estate mogul says there is a decent chance that he will mount a third-party bid for the White House.

"The RNC (Republican National Committee) has not been supportive," Trump said in a 40-minute interview with The Hill ahead of his Thursday trip to the U.S.-Mexican border. "They were always supportive when I was a contributor. I was their fair-haired boy. The RNC has been, I think, very foolish."

Trump is leading the rest of the 16-candidate GOP pack in nearly every Republican primary poll, though a Quinnipiac University survey from this week found voters in the swing states of Colorado, Iowa and Virginia gave him negative approval ratings compared to other candidates. And when matched up head-to-head against Democratic front-runner Hillary Clinton, Trump is one of the worst-performing candidates.

"I'm surprised that I'm this high," Trump said.

He told The Hill that "so many people" want him to run as a third-party candidate if he doesn't win the Republican Party nomination.

"I'll have to see how I'm being treated by the Republicans," the 69-year-old said. "Absolutely, if they're not fair, that would be a factor."

GOP leaders and presidential contenders have voiced concern that Trump's controversial comments, including some made about Mexican immigrants being rapists, are tarnishing the Republican Party's image. However, his poll performance suggests that he is exciting the party base more than anything.

Reince Priebus, the RNC chairman, called Trump earlier this month to ask that he dial back his rhetoric on immigration.

More recently, the RNC issued a statement rebuking Trump for saying that Sen. John McCain, R-Ariz., is not a war hero, before saying that he is only a war hero because he was captured. That comment also pushed several Republican presidential contenders to call for Trump to withdraw from the race.

"I'm not in the gang," Trump told The Hill. "I'm not in the group where the group does whatever it's supposed to do. I want to do what's right for the country - not what's good for special interest groups that contribute, not what's good for the lobbyists and the donors."

Despite their concern and anger over Trump, Republican debate organizers have said they are powerless to prevent him from participating in the upcoming GOP debates hosted by Fox News, the first of which is scheduled for Aug. 6 and will feature the top 10 best-polling candidates.

"The RNC by law cannot remove anyone from a debate, nor can it insert anyone into a debate," said Sean Spicer, the GOP's chief strategist and spokesman, the National Journal reported.

Any attempt to ban Trump from participating would amount to a "coordinating expenditure" that promotes one candidate over another, which would be a violation of campaign finance rules, Spicer said.