In the long annals of the republic, the White House has seen its share of perfidy and scandal, presidents who cheated on their wives and cheated the taxpayers, who abused their power and abused the public trust.

But not since the framers emerged from Independence Hall on that clear and cool day 236 years ago has any president been voted out of office and then accused of plotting to hold onto power in an elaborate scheme of deception and intimidation that would lead to violence in the halls of Congress.

What makes the indictment against Donald J. Trump on Tuesday so breathtaking is not that it is the first time a president has been charged with a crime or even the second. Mr. Trump already holds those records. But as serious as hush money and classified documents may be, this third indictment in four months finally gets to the heart of the matter, the issue that will define the future of American democracy.

At the core of the United States of America vs. Donald J. Trump is no less than the viability of the system constructed in that summer in Philadelphia. Can a sitting president spread lies about an election and try to employ his government’s power to overturn the will of the voters without consequence? The question would have been unimaginable just a few years ago, but the Trump case raises the kind of specter more familiar in countries with histories of coups and juntas and dictators.

The framers considered the peaceful transfer of power fundamental to the new form of government they were devising. It was a fairly radical innovation in its day, an era when kings and emperors generally gave up power only upon natural death or at the point of a weapon. In the newborn republic, by contrast, the framers set limits on power through four-year presidential terms renewable only by the voters.

George Washington established the precedent of voluntarily stepping down after two of those terms, a restraint later incorporated into the Constitution through the 22nd Amendment. John Adams established the precedent of surrendering power after losing an election. Ever since, every defeated president accepted the verdict of the voters and stepped down. As Ronald Reagan once put it, what “we accept as normal is nothing less than a miracle.”

Until Mr. Trump came along. For all of the many, many allegations made against Mr. Trump on all sorts of subjects during his time on the public stage, everything else feels small by comparison. While he failed to keep his grip on power, Mr. Trump has undermined the credibility of elections in the United States by persuading three in 10 Americans that the 2020 election was somehow stolen from him even though there is no evidence of that and many of his own advisers and even some members of his own family do not believe it.

Bringing the case to court, of course, may or may not restore some of that public faith in the system. Millions of Mr. Trump’s supporters and many Republican leaders have embraced his narrative of victimization, dismissing the prosecution without waiting to read the indictment as merely part of a far-reaching, multi-jurisdictional and sometimes even bipartisan “witch hunt” against him.

Mr. Trump has been laying the ground for the eventual indictment for months, making clear to his backers that they should not trust anything prosecutors tell them. “Why didn’t they do this 2.5 years ago?” Mr. Trump wrote on his social media page on Tuesday afternoon. “Why did they wait so long? Because they wanted to put it right in the middle of my campaign. Prosecutorial Misconduct!”

That is a political defense, not a legal one, but one that so far has succeeded in preserving his electoral standing in his comeback campaign for the White House. Despite prognostications to the contrary, the last two indictments succeeded only in enhancing his appeal among Republicans in the contest for the party nomination to challenge President Biden next year.

In a court of law, however, the challenge for Mr. Trump will be different, especially with a jury selected from residents of Washington, a predominantly Democratic city where he won just 5 percent of the vote in 2020. Mr. Trump’s strategy may be to try to delay a trial until after the 2024 election and hope that he wins so that he can short-circuit the prosecution or even pardon himself.

The most essential facts of the case, after all, are not in dispute. Mr. Trump was astonishingly open in declaring that he wanted to overturn the election. Since leaving office, he has even called for the “termination” of the Constitution to reinstall him in the White House immediately without waiting for a new election.

The question is whether the facts add up to crimes as alleged by a federal grand jury at the behest of Jack Smith, the special counsel. Just as no president ever tried to reverse his defeat at the ballot box before, no prosecutor has brought charges for doing so, meaning there is no precedent for applying the statutes on the books to such a circumstance.

Mr. Trump’s defenders argue that he had good-faith reasons for contesting the election results in multiple states and that he did nothing more than pursue his legitimate, legal options. What Mr. Smith is doing, they maintain, is criminalizing a political dispute in a way that amounts to victor’s justice — Mr. Biden’s administration punishing his vanquished foe.

But as testimony in the bipartisan congressional investigation into the Capitol attack of Jan. 6, 2021, demonstrated, Mr. Trump was told over and over again by his own advisers, allies and administration officials that the allegations he was making were not true, and yet he publicly continued to make them, sometimes just hours later.

He was told they were not true by not one but two attorneys general, multiple other Justice Department officials and the government’s election security chief — all his appointees. He was told by his own campaign officials and the investigators they hired. He was told by Republican governors and secretaries of state and legislators.

Despite all that, he has never backed down in the two and a half years since, even as assertion after assertion has been debunked. Not a single independent authority who was not allied with or paid by Mr. Trump — no judge, no prosecutor, no election agency, no governor — has ever validated any substantial election fraud that would have come close to reversing the results in any of the battleground states, much less the three or four that would be required to change the winner.

Instead, Mr. Trump is the one facing charges that he attempted to defraud the United States with bogus claims that he had every reason to know were bogus, all in a bid for power. He will argue that this is all politics and that he should be returned to office in next year’s election.

And so now the justice system and the electoral system will engage in a 15-month race to see which will decide his fate first — and the country’s. The real verdict on the Trump presidency is still to come.