WASHINGTON -- Presidential candidate Donald Trump ruled out the prospect of a third-party White House bid Thursday and vowed to support the Republican Party's nominee - whoever it may be.
The billionaire businessman announced his decision in a raucous news conference at Trump Tower, the gold-hued skyscraper in midtown Manhattan where he launched his surging and front-running campaign for president.
"I have signed the pledge," Trump said, adding that he intends to win the nomination himself and face whoever the Democrats nominate.
"So, I will be totally pledging my allegiance to the Republican Party and the conservative principles for which it stands, and we will go out and we will fight hard and we will win," he said.
Trump's decision comes weeks after he roiled the race for the GOP nomination when, in response to the first question at the opening debate of the 2016 campaign, he refused to promise to back the party's nominee if he fell short.
He was intensely lobbied by Republican National Committee leaders, who have struggled to rein in the unpredictable former reality television star. Trump announced his decision shortly after meeting privately with RNC Chairman Reince Priebus.
Kentucky Sen. Rand Paul, who angrily challenged Trump at the debate, took credit for what he termed the billionaire's "capitulation."
"I spent the last few weeks making sure people knew it was not acceptable to potentially throw the next election to Hillary," Paul wrote on Twitter, referring to Democratic front-runner Hillary Rodham Clinton.
The decision puts an end - for now - to the nervousness felt inside the GOP about the prospect of Trump holding firm and keeping his options open. At the debate, he said that gave him "a lot of leverage."
The pledge is not legally binding. Trump could always change his mind, particularly if GOP establishment leaders take aggressive steps to thwart his candidacy in the coming months.
"I see no circumstances under which I would tear up that pledge," Trump said Thursday.
If not for Trump, the need for such a loyalty oath probably would not exist. There were no doubts about the intentions of the GOP's other major presidential contenders headed into the debate, and they quickly lined up Thursday to sign.
"The RNC clearly felt it had to box Trump into a decision," said Doug Watts, a spokesman for fellow candidate and retired surgeon Ben Carson. "We just sort of shrugged our shoulders, and that's the end of that."
A third-party bid by Trump could harm the GOP's efforts to take back the White House after eight years of Democratic President Barack Obama. He leads the Republican field in what are still very early polls.
RNC officials had been working with Trump's campaign to avoid such a scenario. In recent days, Trump hinted the lobbying was beginning to work. "I think a lot of people are going to be very happy," he said Saturday in Tennessee.
The RNC's pledge asks candidates to promise to "endorse the 2016 Republican presidential nominee regardless of who it is." Further, it asks them to pledge "that I will not seek to run as an independent or write-in candidate, nor will I seek or accept the nomination for president of any other party."
"It is, more than anything, your word," former technology executive Carly Fiorina said Thursday on CNN's "New Day." ''And I would presume that somebody running for president would like to signal to the American people, and most especially right now to Republican primary voters, that their word can be trusted."
Trump signs pledge to back GOP's 2016 presidential nominee