Donald Trump pledged to support the Republican presidential nominee in the general election  Thursday afternoon, effectively ruling out a third-party bid, The Post’s Robert  Costa reports.

The move will calm some nerves within the GOP about Trump’s unusual approach to campaigning for the White House, if only temporarily. As the party’s current 2016 front-runner, Trump has defied expectations and continues to experience a healthy polling lead over his rivals despite a series of controversial remarks that might sink a more traditional candidate.

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Whether Trump will abide by the pledge is another question, and his trustworthiness on the matter was greeted by skepticism Thursday. Here’s how Costa described his decision and his comments at a news conference in New York City:

The promise, which Trump has long avoided making, brings him closer to a party whose rank-and-file activists he has thrilled this summer but 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 standard-bearer …

“I will be totally pledging my allegiance to the Republican Party and the conservative principles for which it stands,” Trump said as he was surrounded by backers holding “TRUMP” posters next to his eponymous 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.

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

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The Pledge #MakeAmericaGreatAgain

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The Republican presidential field started responding on social media by late Thursday afternoon. Here’s how GOP candidates weighed in:

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