MIAMI - Donald Trump became the first former president to face a judge on federal charges as he pleaded not guilty in a Miami courtroom Tuesday to dozens of felony counts accusing him of hoarding classified documents and refusing government demands to give them back.

The history-making court date, centered on charges that Mr. Trump mishandled government secrets that as commander-in- chief he was entrusted to protect, kickstarts a legal process that will unfold at the height of the 2024 presidential campaign and carry profound consequences not only for his political future but also for his own personal liberty.

Mr. Trump approached his arraignment with characteristic bravado, posting social media broadsides against the prosecution from inside his motorcade en route to the courthouse and insisting — as he has through years of legal woes — that he has done nothing wrong and was being persecuted for political purposes. But inside the courtroom, he sat silently, scowling and arms crossed, as a lawyer entered a not guilty plea on his behalf in a brief arraignment that ended without him having to surrender his passport or otherwise restrict his travel.

The arraignment, though largely procedural in nature, was the latest in an unprecedented reckoning this year for Mr. Trump, who faces charges in New York arising from hush money payments during his 2016 presidential campaign as well as ongoing investigations in Washington and Atlanta into efforts to undo the results of the 2020 race.

Always in campaign mode, he swiftly pivoted from the solemn courtroom to a festive restaurant, stopping on his way out of Miami at Versailles, an iconic Cuban spot in the city’s Little Havana neighborhood where supporters serenaded Mr. Trump, who turns 77 on Wednesday, with “Happy Birthday.” The back-to-back events highlight the tension for Mr. Trump in the months ahead as he balances the pageantry of campaigning with courtroom stops accompanying his status as a twice-indicted criminal defendant.

Yet the gravity of the moment was unmistakable.

Until last week, no former president had ever been charged by the Justice Department, let alone accused of mishandling top-secret information. The indictment unsealed last week charged Mr. Trump with 37 felony counts — many under the Espionage Act — that accuse him of illegally storing classified documents in his bedroom, bathroom, shower and other locations at Mar-a-Lago and trying to hide them from the Justice Department as investigators demanded them back. The charges carry a yearslong prison sentence in the event of a conviction.

Mr. Trump has relied on a familiar playbook of painting himself as a victim of political persecution. He attacked the Justice Department special counsel who filed the case as a “thug” and “deranged,” pledged to remain in the race no matter what and addressed supporters Tuesday night at his Bedminster, N.J., golf club, where he delivered a roughly half-hour speech full of repeated falsehoods and incendiary rhetoric and threatened to go after President Biden and his family if elected.

“The seal is broken by what they’ve done. They should never have done this,” Mr. Trump said of the indictment.

But Attorney General Merrick Garland, an appointee of President Biden, sought to insulate the department from political attacks by handing ownership of the case last November to a special counsel, Jack Smith, who on Friday declared, “We have one set of laws in this country, and they apply to everyone.”