Donald Trump again refuses to rule out independent bid 'in case I don't get treated fairly'
Real estate mogul Donald Trump (AFP Photo/Kena Betancur)

Real-estate magnate Donald Trump, who tops the polls in the Republican presidential nomination race, doubled down Tuesday on his insistence he would "keep the door open" to a potential independent run.

The brash billionaire stunned viewers and fellow Republican candidates last week during their party's first debate of the 2016 presidential campaign by saying he would not rule out a third-party candidacy -- a nightmare scenario for the Republicans.

But after days of controversial statements in the wake of the debate, including a series of comments and tweets seen by many as sexist and offensive, Trump returned to the idea of running for president outside the Republican Party.

"We're going to keep the door open," Trump told Fox News in a telephone interview.

"I want to run as a Republican," he added. "But I do want to keep that door open in case I don't get treated fairly."

Political experts and observers have stressed that an independent Trump candidacy could spell disaster for Republicans because such a move would likely split the GOP vote and hand an election victory to likely Democratic nominee Hillary Clinton.

The former secretary of state meanwhile offered a blunt criticism of Trump, saying on the campaign trail Monday that he went "way overboard" in his crude verbal assault on a female journalist.

Popular Fox News moderator Megyn Kelly used tough tactics when questioning Trump during last Thursday's debate, particularly when asking him about having called women "dogs" and "fat pigs."

A day later Trump told CNN that Kelly had "blood coming out of her wherever," a remark taken by many to suggest Trump thought Kelly was tough on him because she was menstruating.

Trump also took a swipe at the American campaign finance system in general, suggesting too much money being donated to candidates leaves politicians in debt to donors.

"I used to be those people. I would give to everybody," Trump said.

"Those people that put up the money, those are not people that are not expecting big, big things. And some of those things are counter to what's good for the country," Trump added.

The mogul stressed that because of his vast wealth he could not be bought by donors or special interests.

"I don't need money, I'm running my own deal," Trump said.

"I have no special interests behind me."