Business mogul and presidential candidate Donald Trump announced Friday he signed the loyalty pledge that the Republican National Committee has demanded of its candidates. (Reuters)

Donald Trump on Thursday signed a loyalty pledge to the Republican Party -- and, with that, the renegade candidate became a little less of a renegade and a party establishment unsure of what to do with the bedeviling front-runner brought him more fully into its embrace.

The document the GOP presidential front-runner signed promises that he will support the Republican nominee in next year’s general election, effectively ruling out a third-party or independent run.

“I will be totally pledging my allegiance to the Republican Party and the conservative principles for which it stands,” Trump said at an event at Trump Tower in New York, surrounded by backers holding “TRUMP” posters next to the skyscraper’s steep elevators. He held up the single sheet of paper with his name scribbled in thick black marker. “We will go out and fight hard, and we will win. We will win,” he said.

The bustling scene, attended by a crowd of reporters and television cameras, was more political theater than the marking of a formal pact, since Trump is under no legal obligation to abide by the political document.

But the promise, which Trump has long avoided making, does bring him closer to a party whose rank-and-file activists he has thrilled this summer and whose leadership has at times viewed his rapid ascent with alarm — especially the prospect of an outside bid that could siphon away votes from the eventual Republican standard-bearer.

By bringing Trump more fully within the party’s tent, Republicans gain reassurance about his intentions — and court possible fallout for working closely with the unpredictable and sharp-tongued billionaire, who has angered Hispanic leaders with his controversial comments on illegal immigration.

Trump made his announcement at an afternoon news conference after meeting with the loyalty statement’s author, Republican National Committee chairman Reince Priebus, whose relationship with the mogul has been cordial but delicate since Trump entered the 2016 race.

He said that he sees “no circumstances under which I would tear up that pledge. ... I have no intention of changing my mind.”

Watching the slightly surreal drama of this odd-couple alliance play out on the airwaves, veteran GOP voices expressed discomfort about the way the Republican Party is trying to manage Trump, and with the power Trump is accumulating within the party. Priebus’s travel to Trump Tower spoke volumes, several said.

“They’re bowing at the altar of Trump Tower,” said Pete Wehner, a former adviser to President George W. Bush. “Trump is in control... It looks like the RNC is going hat in hand to Trump. It doesn’t help the RNC. It simply helps Trump.”

Said former RNC chairman Michael Steele: “I would have preferred that Trump met [Priebus] at the RNC, but I don’t know the circumstances that required him to do what he did.”

Trump’s latest embrace of the Republican Party is a conundrum not only for the RNC, but for Trump’s rivals. Many of them are pleased that the businessman’s third-party threat has for the moment been diminished, but they know that urging him to do so also means pressure on them to make the same oath, pledging to back whoever wins the nomination, even Trump.

Former Florida governor Jeb Bush, appearing Thursday on ABC’s “Good Morning America,” said that “of course” he would back Trump, should he emerge triumphant at next year’s GOP convention in Cleveland. “We need to be unified, we need to win,” Bush said.

But Bush indicated that he is not entirely comfortable with the possibility: “I think Mr. Trump ought to figure out a way maybe to lessen the divisive language, the hurtful language and talk about the aspirations of the American people rather than trying to prey on their fears.”

Appearing Thursday on CNN, Sen. Rand Paul (R-Ky.) shrugged and said he would “support whoever the nominee is,” but believes “Donald Trump would be a disaster for the country.”

Priebus flew to New York early Thursday from Washington with Sean Spicer, the GOP’s chief strategist, where he met one-on-one with Trump at 1 p.m. About an hour later, Trump addressed the throngs that had gathered in the building’s lobby. Behind him were supporters toting signs, one of which read, “The silent majority stands with Trump.”

Priebus, who arrived quickly at Trump Tower and did not take questions, did not appear alongside Trump at the news conference, but did leave with the signed pledge in hand. At the start, Trump said “The chairman just left, as you probably know” — and there were audible boos.

“The chairman asked if he could come up,” Trump told reporters Thursday. He said he was “greatly honored” by the gesture and that Priebus has been “extremely fair. The RNC has been absolutely terrific.” Looking back at his history with the GOP, Trump said he was for decades a “fair-haired boy” as a top party donor, then became an “outsider” once he launched his campaign. After signing the pledge, he suggested that any lingering tensions have mostly abated.

“I got nothing,” Trump said. “The question was, what did I get for signing the pledge? Absolutely nothing, other than the assurance that I would be treated fairly. And I’ve seen that over the last two months, where they really have been very fair.”

The RNC and Trump’s advisers had been in contact for at least a week about the pledge, working together on the timing of the roll-out, as well as reassuring Trump that the party wants to engage with him and treat him as they would any other candidate, according to Republicans familiar with the talks.

Those Republicans requested anonymity to discuss private conversations. They also said that if his relationship with the RNC should ever sour, he could consider reneging.

Trump’s ties to the party have been bolstered as he has risen in the polls.

In July, Priebus asked Trump to tone down his immigration rhetoric, a suggestion Trump has mostly ignored as he has railed against “anchor babies” — the children of people who immigrate illegally into the United States and give birth here to ensure U.S. citizenship for their child — and called to build a massive wall along the U.S.-Mexico border. Last month, Priebus called Trump a “net positive” for the party who brings a lot of interest in the Republican field.”

As they improved relations, Republican leaders had been trying to prevent Trump from permanently leaving open the possibility of running as an independent candidate if he does not win the Republican nomination. In the Aug. 6 debate in Cleveland, Trump memorably refused to rule out a third-party run, though he had since then signaled a possible change of heart as some state parties were requiring loyalty oaths as a condition of appearing on their state’s primary ballots.

RNC staffers reached out earlier this week to all of the GOP presidential campaigns requesting that their candidates sign a document pledging fealty to the party’s nominee.

Earlier Thursday, Trump explained his thinking in an interview with conservative radio show host John Fredericks: “Look, my number one thing is to win, and the best way to win is as a Republican,” he said. “The third party thing is a tough thing, it’s a tough route. And I believe that it can be done, but it’s a tougher route, it’s a riskier route.”

On Twitter after Trump’s decision was announced, Bush and Paul chided him. “Voted Republican since 1972,” Bush scribbled on a piece of paper captured in a photograph he shared, a nod toward Trump’s past associations and donations to Democrats. Paul wrote that Trump “capitulated” following criticism from the Kentucky senator.

In Manhattan, Trump, too, took shots. As with almost every Trump forum, he relished the chance to snipe at his competitors, this time from a lectern on his home turf. Reacting to Bush’s remarks to ABC, Trump said, “It’s a little bit sad. ... He just doesn’t have the energy.” He again knocked Bush for speaking Spanish on the campaign trail: “I think that when you get right down to it, we are a nation that speaks English. And I think while we’re in this nation, we should be speaking English.”

And there was unexpected spectacle.

After wrapping up the news conference, and the cable networks were about to cut away, Trump ushered over a man he described as the “speaker of the house in Indonesia.” Trump asked him, “Do they like me in Indonesia?”

The visiting speaker, Setya Novanto, nodded and smiled. “Yes,” he said, chuckling. Trump then strolled off, waving farewell.

Philip Rucker contributed reporting.