WASHINGTON - Thanks to Texas, Mitt Romney can finally drop the word "presumptive" from his title. More than five years after launching his first campaign for the presidency, the former Massachusetts governor on Tuesday night clinched the Republican nomination by winning the largely uncontested Texas primary, the Associated Press projected. The achievement completes what for Romney has been an arduous process of winning over skeptical conservatives and projecting himself as the party's most competitive choice for taking on President Obama in the fall. The former Massachusetts governor surpassed the 1,144-threshold to become the nominee by winning at least 88 delegates in Texas, according to the Associated Press tally. The victory is a formality, as most of his Republican opponents had long since peeled away from the race - and then gradually crossed over to endorse Romney. As the party's nominee, Romney now faces the challenge of unseating an incumbent president whose numbers are still fairly strong against Romney despite the country's lingering economic problems. "I am honored that Americans across the country have given their support to my candidacy and I am humbled to have won enough delegates to become the Republican Party's 2012 presidential nominee," Romney said in a written statement. Obama's campaign has also aggressively gone after Romney with a string of attack ads and web videos in recent weeks. Romney, in an interview with Fox News before Tuesday's primary, accused Obama of leading a "personal attack campaign" against him. "He's going after me as an individual," Romney said. But he pointed to his own economic experience in making his case for the job. "I have experience in the economy that's going to help me get good jobs for Americans, so we can be secure again," Romney told Fox News. Romney spent Tuesday evening at a Las Vegas fundraiser with celebrity real estate mogul Donald Trump, who has been renewing discredited suggestions that Obama wasn't born in the United States. Romney says he believes Obama was born in the U.S. but hasn't condemned Trump's repeated insinuations to the contrary. The Obama campaign released a video Tuesday criticizing Romney's unwillingness to stand up to Trump and the more extreme elements in his party. Republicans won't officially nominate Romney until late August at the Republican National Convention in Tampa, Florida. Libertarian-leaning Texas Rep. Ron Paul said on May 14 he would no longer compete in primaries, though his supporters are still working to gain national delegates at state conventions.