CLEVELAND - The Republicans set in motion a key ritual of the American political process Thursday, with billionaire businessman Donald Trump using the opening moments of the party's first debate of the 2016 presidential campaign by refusing to rule out running as an independent.
At centre stage, the Republican frontrunner was the only one of 10 candidates to raise his hand when the Fox News hosts asked if anyone onstage would not pledge to support the eventual party nominee.
"I will not make the pledge at this time," Trump said.
Trump, who brushed aside questions about his public denigration of women and said he had done nothing but used American laws when his companies took bankruptcy, put to rest speculation he would tone down his rhetoric.
Trump's refusal to take the pledge enraged Kentucky Sen. Rand Paul, who said Trump was "already hedging his bets because he's used to buying politicians."
Through the remainder of the debate, the candidates made little news, choosing instead to use their time in the two-hour session to repeat already well-known positions.
But Trump stood out for his willingness to stand behind many of his past statements that many expected would be ruinous to his campaign. Instead he has been rising rapidly in the polls to become the front-runner.
Fifteen months from the election, Trump remains a longshot candidate to replace President Barack Obama. But the brash real estate mogul and reality television star took centre stage in Cleveland, Ohio, as top performer in several recent national polls. Only 10 of 17 Republican candidates were invited to participate in the main event, with the remaining seven relegated to a pre-debate forum.
It was a key test for Trump, whose unpredictable style and unformed policy positions mean he doesn't fit neatly into any single wing of the Republican Party.
That appears to be a draw to some Republicans frustrated with Washington and career politicians, but others fear his eccentricities and outlandish comments - whether about Mexican immigrants being "criminals" and "rapists" or his questioning of the war record of Sen. John McCain - will taint the American public's view of the party.
Standing to Trump's left on the debate stage Thursday night was former Florida Gov. Jeb Bush, a favourite of the wealthy donors and business leaders that populate the establishment wing of the Republican Party. But Bush, the son and brother of two former U.S. presidents, has struggled to separate himself from the rest of the field and he faces questions about whether his nomination would mark a return to the past.
Immigration and counterterrorism dominated the early stages of the debate, two issues that highlight the deep divisions within the Republican Party.
Bush, whose wife was born in Mexico, defended his call for a path to legal status for some of the people living in the U.S. 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. He said Thursday border patrol agents agreed with his comments about Mexicans, and he took credit for immigration being an issue in the2016 campaign.
Paul and New Jersey Gov. Chris Christie engaged in a heated exchange over the USA Patriot Act and laws giving government access to Americans' phone records.
Christie, a former U.S. attorney, said he was the only person on the stage to file applications under the Patriot Act and gone before secretive courts for authority.
Paul, a staunch opponent of the surveillance programs, said he wanted to collect more records from terrorists, not law-abiding Americans.
To Trump's right was Wisconsin Gov. Scott Walker, whose victories over labour unions in his home state created his national profile.
Florida Sen. Marco Rubio, the youngest candidate in the field at age 44, was trying to carve out a niche as a foreign policy expert, but has struggled to break through this summer - particularly since Trump's surge.
The remaining seven candidates who didn't make the cut for Thursday night's main debate were relegated to a pre-debate forum, a low-key event in a largely empty arena, where candidates avoided debating each other and largely stuck to scripted responses on domestic and foreign policy.
Former Texas Gov. Rick Perry and businesswoman Carly Fiorina opened the early event with biting criticisms of Trump.
Perry - whose failed 2012 White House campaign was damaged by an embarrassing debate stumble - accused Trump of using "his celebrity rather than his conservatism" to fuel his run for president.
Fiorina, the only woman in the Republican field, said Trump had tapped into Americans' anger with Washington, but she challenged the businessman as lacking policy positions. "What are the principles by which he would govern?" she asked.
While the candidates pitched their visions for the Republican Party's future, they also were making the case that they would present the strongest general election challenge to Hillary Rodham Clinton, the front-runner for the Democratic nomination.
Thursday's debate is the first of six Republican Party-sanctioned debates scheduled before primary voting begins in February.
The Democratic National Committee, meanwhile, released plans for its presidential debates, announcing the first of six will be held Oct. 13 in Nevada.
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Associated Press writers Steven R. Hurst and Julie Pace reported from Washington. Steve Peoples reported from Cleveland.
