File photo of Donald Trump.
Fresh post-debate polls show real-estate magnate Donald Trump holding his lead Tuesday over rival Republican presidential contenders, even as he insisted he will "keep the door open" to a potential independent run.
But the surveys contained mixed news for the brash billionaire, notably that voters are increasingly uncomfortable with his aggressive temperament.
A new Suffolk University poll in Iowa, which holds the first presidential contest early next year, has Trump leading with 17 per cent support, Scott Walker, governor of neighboring Wisconsin, in second with 12 per cent and Senator Marco Rubio of Florida with 10.
The survey also showed Jeb Bush, the politician with perhaps the highest name recognition in the broad Republican field, slipping to seventh spot, compared to his RealClearPolitics average of third position in Iowa over the past month.
But in a warning of sorts to Trump, who sparked controversy during and after last week's first major Republican presidential debate, 55 per cent of Suffolk respondents said his debate performance made them "less comfortable" with Trump as a candidate.
In Rasmussen Reports' new Tuesday poll, Trump held the lead at 17 per cent -- a significant drop from the 26 per cent he enjoyed in the same national poll conducted late last month.
Rubio and Bush were in second with 10 per cent, one point ahead of Walker and former Hewlett-Packard boss Carly Fiorina, who surged from the back of the pack after her breakout debate performance last week.
In a new Franklin Pearce University/Boston Herald poll in New Hampshire, Trump led with 18 per cent support, although 41 per cent said they do not think he has the temperament to be president.
Bush came second with 13 per cent, while Ohio Governor John Kasich, who had previously polled poorly, surged to claim 12 per cent.
Fiorina earned nine per cent in Iowa and seven in New Hampshire.
As the new poll data rolled out, Trump doubled down on his assertion, made at last Thursday's debate, that he would not rule out a third-party candidacy -- a nightmare scenario for the Republicans.
Independent Trump? "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 the 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 many construed as referring to menstruation.
Kelly was not mentioned in Fox's Tuesday Trump interview.
The Donald took a swipe at the American campaign finance system in general, suggesting too much money being donated to candidates like Bush 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," Trump added.
"That's not really a good thing for the system."
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.