Trump won't rule out third-party run

Republican 2016 US presidential candidate businessman Donald Trump answers a question at the first official Republican presidential candidates debate of the 2016 US presidential campaign in Cleveland, Ohio, August 6, 2015. [Photo/Agencies]

Setting a combative tone from the start, billionaire businessman Donald Trump took the spotlight in the first Republican presidential debate on Thursday, declaring he would not commit to supporting the party's eventual nominee and would not rule out running as a third-party candidate.

"I will not make the pledge at this time," Trump said. He also refused to apologize for making insulting comments about women, saying, "The big problem this country has is being politically correct."

Kentucky Sen. Rand Paul immediately jumped in to challenge Trump on his refusal to commit to supporting the party nominee.

"He's already hedging his bets because he's used to buying politicians," Paul said.

Trump's blunt style was in line with the approach he's taken to his campaign throughout the summer, appealing to voters frustrated with career politicians and perplexing his rivals. He entered the first debate leading the polls in a field filled with governors and senators.

Most of the candidates on the stage in Cleveland, Ohio, avoided engaging directly with Trump in the debate's early moments. While 17 Republicans are seeking the party's nomination, only 10 were invited by debate host Fox News to participate in the main event based on their showing in recent polls.

Former Florida governor Jeb Bush, a favorite of the party's establishment wing, defended his call for a path to legal status for people living in the United States illegally. It's an unpopular position among some Republican voters who equate legal status with amnesty.

"The great majority of people coming here have no other option," Bush said.

Trump in particular has pushed the issue of immigration throughout the summer, drawing criticism for calling Mexican immigrants rapists. He said Thursday that he had been told that by Border Patrol agents, and he took credit for immigration being an issue in the2016 campaign.

"If it weren't for me, you wouldn't even be talking about illegal immigration," he said.

To Trump's right on the stage was Wisconsin Governor Scott Walker, whose victories over unions in his home state created his national profile. Florida Senator Marco Rubio, the youngest candidate in the field at age 44, is trying to carve out a niche as a foreign policy authority but has struggled to break through this summer, particularly since Trump's surge.