Cleveland - A man badly in need of a big moment, Donald Trump on Thursday faced the most important speech of his presidential campaign, a last chance to make his case to sceptics at a convention marked by divided loyalties and unwanted distractions.The newly crowned Republican nominee had hoped for a triumphant turn at the podium, but he has instead been plagued by fresh political and policy headaches: His most tenacious primary rival, Senator Ted Cruz, still refused to endorse him - and happily took the convention stage anyway. And Trump's own exposition of his foreign policy views was rattling allies at home and abroad.The candidate said he just wanted people to come out of the Republican National Convention knowing this fact: "I'm very well-liked." But it is clear he'll need more than that if he is to end his four days in the spotlight achieving more good than harm.Trump raised the stakes in an interview in which he said he would set new conditions before coming to the aid of Nato allies. The remarks, in an interview published on Thursday with The New York Times, deviated from decades of US foreign policy doctrine and seemed to suggest he would put new conditions on the 67-year-old alliance's bedrock principle of collective defence.As president, Trump said he would defend an ally against Russian aggression only after first ensuring that the allies had met their obligations to the US. "If they fulfil their obligations to us, the answer is yes," he said.The comment put a finer point on the candidate's previous criticism of Nato's relevance and his contention that allies aren't paying their fair share. It served up a fresh reminder of why Trump is such a hard nominee to swallow for many in the GOP establishment.Intra-party divisionsIntra-party divisions were sharply on display on Wednesday night in a hall that echoed first with cheers for Trump's fiercest opponent in the primaries, Texas' Cruz, then thunderous boos from the pro-Trump masses when Cruz wrapped up his speech without endorsing the nominee.Trump allies were furious. New Jersey Governor Chris Christie called Cruz "totally selfish". Trump's son Eric Trump, on CBS' This Morning, labelled it "classless".The candidate himself tweeted: "No big deal!" But he later said Cruz did not honour the pledge that Republican primary candidates had made to support the eventual nominee.The gathering's open secret was that Cruz came to the convention to audition for 2020 - an ambition that largely counts on Trump losing this year.Beyond that, the two men have a history of animosity. The businessman has called the senator "Lyin' Ted" and the senator branded Trump a "pathological liar" and "serial philanderer".No surpriseBoth Cruz and the Trump campaign acknowledge that Wednesday night wasn't a surprise. The campaign saw his remarks ahead of time and still wanted him to speak. Cruz said on Thursday he assumes the reason for that is they think it will encourage people to vote.Speaking to members of the Texas delegation, Cruz held his ground. He moved no closer to an endorsement, saying only that he, too, will be watching and listening on Thursday night. He said he'll vote for the "candidate I trust to defend our freedom and be faithful to the Constitution". He insisted he would not be a "servile puppy dog", especially after Trump's criticism of the senator's wife and father.The episode has made it harder for Trump's vice presidential pick, Indiana Governor Mike Pence, a favourite of conservatives who have decidedly mixed feelings about Trump, to make much of a splash.Pence made a plea for unity in his speech on Wednesday night, but he found himself having to defend Trump's foreign policy comments hours later.In an interview on Fox News, he insisted on Thursday morning that Trump would stand by US allies despite the remarks, but he added that "those countries must pay their fair share".'Maybe, maybe not'The Clinton campaign said Trump's message to Nato allies was really, "Maybe, maybe not.""Ronald Reagan would be ashamed. Harry Truman would be ashamed," Clinton adviser Jake Sullivan said in a statement. "Republicans, Democrats and independents who helped build Nato into the most successful military alliance in history would all come to the same conclusion: Donald Trump is temperamentally unfit and fundamentally ill-prepared to be our commander in chief."Republican Senator Lindsey Graham, another vanquished Trump rival, said the comments "make the world more dangerous and the United States less safe". He called on Trump to clarify on Thursday night when "the world is watching".The campaign had hoped Pence's address would quiet Republican qualms about Trump.But Cruz' appearance left the arena unsettled for the night's closing speakers. Former house speaker Newt Gingrich tried to quiet the anger as he took the stage, going off script to try to explain away the senator's lack of support for the nominee."Ted Cruz said you can vote your conscience for anyone who will uphold the Constitution," Gingrich said. "In this election there is only one candidate who will uphold the Constitution."