When President Trump steps before a judge this week to be arraigned in a New York courtroom, it will not only mark the first time a former American president has faced criminal charges. It will also be a reckoning for a man long nicknamed “Teflon Don,” who until now has managed to skirt serious legal jeopardy despite 40 years of legal scrutiny.

Mr. Trump, who is the early front-runner for the Republican presidential nomination, is expected to turn himself in Tuesday. He faces charges including at least one felony offense reportedly related to hush money payments to women during his 2016 campaign. Like any other person facing trial, he will be booked, fingerprinted and photographed before being given the chance to enter a plea.

Mr. Trump’s office said Sunday that he would “deliver remarks” from Mar-a-Lago following the arraignment, which is expected to take place at 2pm New York time. Speaking on ABC’s “This Week” Sunday, Mr. Trump’s lawyer, Joe Tacopina, said the former president’s surrender will be as “painless and classy” as possible.

The spectacle that is sure to unfold will mark an unprecedented moment in American history that will demonstrate once again how dramatically Mr. Trump — who already held the distinction of being the first president to be impeached twice — has upended democratic norms. But on a personal level, the indictment pierces the cloak of invincibility that seemed to follow Mr. Trump through his decades in business and in politics, as he faced allegations of fraud, collusion and sexual misconduct.

“Boy, after all this time it’s a bit of a shock,” Trump biographer Michael D’Antonio said of the indictment. “You know I always thought of him as the Gingerbread Man, shouting, ‘You can’t catch me!’ as he ran away.”

“Given his track record,” he said, “I had trouble imagining he would ever be held accountable.”

“These are not things that Donald Trump ever thought in his entire life, nor I, for that matter, that he would ever be confronted with,” Trump’s longtime fixer and a key witness in the case who served jail time for the payments, Michael Cohen, told CNN.

Of course, some of the celebration by Mr. Trump’s detractors may be premature. Mr. Trump could seek to have a judge quickly dismiss the case. Even if it moves forward, there’s no guarantee of conviction. Intensifying investigations in Atlanta and Washington are seen as potentially more serious legal threats.

Mr. Trump and his team were caught by surprise when word of the New York indictment broke Thursday evening, following news reports that the grand jury hearing the case was set for a weeks-long hiatus. As the deliberations dragged on, some in Mr. Trump’s orbit had become convinced that the case had stalled and that charges might never be brought. That included Trump lawyer Joe Tacopina, who said Friday morning he had hoped the “rule of law would prevail.”

Mr. Trump, he said on the “Today” show, was “initially was shocked” by news of the charges, but quickly pivoted to his usual pushback playbook.

“After he got over that,” he said, Mr. Trump “put a notch on his belt and he decided we have to fight now. And he got into a typical Donald Trump posture where he’s ready to be combative on something that he believes is an injustice. … I think he’s now in the posture that he’s ready to fight this.”

In the meantime, Mr. Trump and his team have tried to use the news to his advantage, hoping to energize his loyal base by painting the investigation as part of a larger plot to derail his candidacy.

Already, the charges have been a boon to his struggling fundraising. The campaign announced Friday evening that it had raised over $4 million in the 24 hours after the indictment became public, far smashing its previous record after the FBI search of Mr. Trump’s Mar-a-Lago club.

More than 25 percent of donations, according to the campaign, came from first-time donors. The average contribution: $34.

His campaign also continued to blast out supportive statements from dozens of top Republicans who have rallied behind Mr. Trump, including several of his declared and likely challengers, underscoring his continued hold on the party.

Florida’s Governor DeSantis, in a speech Saturday to conservatives meeting in Camp Hill, Pennsylvania, accused the Democratic prosecutor in New York, Alvin Bragg, of weaponizing the law “for political purposes” in bringing a case against “a former president.” Mr. DeSantis said the district attorney had indicted “a former president on misdemeanor offenses” that he was “straining to try to convert into felonies.”

Mr. Trump has been in contact by phone with key congressional allies, including members of House leadership and top committees, according to people familiar with the conversations, who, like others, spoke on condition of anonymity to discuss the response.

Trump ally Jim Banks of Indiana, who formally endorsed the former president Friday, said Mr. Trump “doesn’t back down” and was going to “fight back,” telling a local radio show it was “yet another chapter where Donald Trump is going to come back on top in the end.”

The media maelstrom has catapulted Mr. Trump back into the spotlight he craves, at least temporarily limiting attention being paid to his rivals, including Mr. DeSantis, who is widely expected to challenge Mr. Trump for the nomination, and has been holding events across the county to promote his book.

Trump aides have been discussing other ideas to maximize the situation, including the possibility of holding a press event either before or after the arraignment. Mr. Trump is expected to travel from Florida to New York on Monday and stay overnight at Trump Tower in midtown Manhattan before heading to the courthouse early Tuesday. He will return to Florida after the arraignment.

Mr. Trump has long denied that he had a sexual encounter with the porn actress known as Stormy Daniels and has blasted Mr. Bragg for pursuing the years-old case.

Mr. Trump is also facing continued investigations in Georgia, over his efforts to overturn the results of the 2020 election, and in Washington, where a special counsel is probing the events of January 6, 2021, as well as Mr. Trump’s handling of classified documents at Mar-a-Lago and potential obstruction of the investigation.

But Sam Nunberg, a longtime former aide who broke with Mr. Trump years ago, said that while he no longer supports Trump, he believes the Manhattan case is “a waste of time,” given the allegations, which remain under seal. And he said he was skeptical it would ultimately matter.

“It doesn’t surprise me,” he said of the indictment. “What would surprise me is if he actually ended up behind bars in prison and I don’t see that happening.”

Mr. D’Antonio said that sentiment — and a continued belief that Mr. Trump will somehow prevail and dodge the charges — continues among the many people who have reached out to him in the last 24 hours, despite the charges.

“They’re like, he’s going to get away with it,” he said. “Somehow, he’s going to get it thrown out.”