A Manhattan grand jury voted to indict Donald J. Trump on Thursday for his role in paying hush money to a porn star, according to five people with knowledge of the matter, a historic development that will shake up the 2024 presidential race and forever mark him as the nation’s first former president to face criminal charges.

An indictment will likely be announced in the coming days. By then, prosecutors working for the district attorney, Alvin L. Bragg, will have asked Mr. Trump to surrender and to face arraignment on charges that remain unknown for now.

Mr. Trump has for decades avoided criminal charges despite persistent scrutiny and repeated investigations, creating an aura of legal invincibility that the vote to indict now threatens to puncture.

His actions surrounding his 2020 electoral defeat are now the focus of a separate federal investigation, and a Georgia prosecutor is in the final stages of an investigation into Mr. Trump’s attempts to reverse the election results in that state.

But unlike the investigations that arose from his time in the White House, this case is built around a tawdry episode that predates Mr. Trump’s presidency. The reality star turned presidential candidate who shocked the political establishment by winning the White House now faces a reckoning for a hush money payment that buried a sex scandal in the final days of the 2016 campaign.

Mr. Trump has consistently denied all wrongdoing and attacked Mr. Bragg, a Democrat, accusing him of leading a politically motivated prosecution. He has also denied any affair with the porn star, Stormy Daniels, who had been looking to sell her story of a tryst with Mr. Trump during the campaign.

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Mr. Bragg and his lawyers will likely attempt to negotiate Mr. Trump’s surrender. If he agrees, it will raise the prospect of a former president, with the Secret Service in tow, being photographed and fingerprinted in the bowels of a New York State courthouse.

The prosecution’s star witness is Michael D. Cohen, Mr. Trump’s former fixer who paid the $130,000 to keep Ms. Daniels quiet. Mr. Cohen has said that Mr. Trump directed him to buy Ms. Daniels’s silence, and that Mr. Trump and his family business, the Trump Organization, helped cover the whole thing up. The company’s internal records falsely identified the reimbursements as legal expenses, which helped conceal the purpose of the payments.

Although the specific charges remain unknown, Mr. Bragg’s prosecutors have zeroed in on that hush money payment and the false records created by Mr. Trump’s company. A conviction is not a sure thing: An attempt to combine a charge relating to the false records with an election violation relating to the payment to Ms. Daniels would be based on a legal theory that has yet to be evaluated by judges, raising the possibility that a court could throw out or limit the charges.

The vote to indict, the product of a nearly five-year investigation, kicks off a new and volatile phase in Mr. Trump’s post-presidential life as he makes a third run for the White House. And it could throw the race for the Republican nomination — which he leads in most polls — into uncharted territory.

Mr. Bragg is the first prosecutor to lead an indictment of Mr. Trump. He is now likely to become a national figure enduring a harsh political spotlight.