AFP, Cleveland :Donald Trump continued to dominate the Republican race for US president by causing further controversies in the first debate.The tycoon’s refusal to rule out a third-party run drew boos from the audience on Thursday night.And he stood by offensive comments he has made in the past about women.The 10 candidates in Cleveland, selected by Fox News on the basis of recent national polls, provided a frank and bruising exchange of views.Bombastic, comical, provocative: Donald Trump, the billionaire leading the Republican primary race, offered the best and worst of himself as opponents strained to offer more gravitas in the first major debate of the 2016 campaign.Flanked by nine rivals who trail him in the polls, the real estate mogul immediately set himself apart when he was the only candidate on stage to refuse to pledge that he would back the Republican nominee and not run for president as an independent if he loses the party primary.”I will not make the pledge at this time,” the improbable frontrunner said, to loud boos and jeers from a rambunctious crowd.It was an extraordinary start to the party’s quest to choose a flagbearer for the 2016 race to succeed President Barack Obama, only six months ahead of the first primary votes.By the time the event was over Trump had called US leaders and politicians “stupid,” claimed he had given money to most of the candidates on the stage as well as to top Democrat Hillary Clinton, clashed with Senator Rand Paul and moderators, and said he had no time for “political correctness.”With 17 major Republican candidates in contention, broadcaster Fox News split the debate into two parts, with bottom-tier hopefuls trading barbs in a separate forum ahead of the prime-time event.Trump’s unapologetic, off-script style offends some but has set him apart from a packed field of hopefuls furiously trying to garner the same level of attention.”Donald Trump’s hitting a nerve in this country,” admitted his rival, Ohio Governor John Kasich, during the main event.”For people who want to just tune him out, they’re making a mistake.”Former Florida governor Jeb Bush acknowledged that the bar is likely higher for him in 2016, being the son and brother of two presidents. But he insisted once more that he is his own man with his own policies.”I’m going to have to earn this,” Bush said.He also stood by his earlier remark that immigrants breaking the law to come to the United States did so as an “act of love.”Bush accused Trump of using “divisive” language and warning such verbal sniping will not help Republicans win the White House.The candidates, each looking for a breakout moment, also focused their ire on former secretary of state Clinton, the likely Democratic nominee.”If Hillary is the candidate, which I doubt, that would be a dream come true,” said neurosurgeon Ben Carson, the only African-American candidate in the field.”She is the epitome of the progressive, the secular progressive movement.”Candidates at both the main event and on the debate undercard sought to make an impression on voters — and many aimed at Obama, Clinton and Trump.