President Trump’s indictment on charges of mishandling classified documents at his Florida estate has brought renewed attention to one of the most notable cases in Justice Department history.

The federal charges represent the biggest legal jeopardy so far for Mr. Trump, coming less than three months after he was charged in New York with 34 felony counts of falsifying business records.

Mr. Trump has been charged with seven counts related to the mishandling of classified documents, according to two people familiar with the indictment but not authorized to speak publicly about it.

Mr. Trump’s lawyer James Trusty said Thursday on CNN that the indictment includes charges of willful retention of national defense information, obstruction of justice, false statements and conspiracy.

Mr. Trump, on his Truth Social app, called it “a DARK DAY for the United States of America.” In a video post, he said, “I’m innocent and we will prove that very, very soundly and hopefully very quickly.” Within 20 minutes of breaking the news, his 2024 presidential campaign sent out a fundraising missive telling his followers he’d been indicted and asking for financial support.

WHAT HAPPENS NEXT?

The Justice Department did not immediately publicly confirm the indictment, and any charges were not publicly filed.

Mr. Trump said he’d been summoned to appear in court Tuesday afternoon in Miami. Mr. Trump is reportedly planning to make the appearance, though it is not clear what the procedure would look like.

When he was charged by the Manhattan district attorney in the New York case, Mr. Trump surrendered to authorities, where he was booked behind closed doors and appeared in the courtroom, sitting with his lawyers at the defense table.

HOW DID THIS CASE COME ABOUT?

Officials with the National Archives and Records Administration reached out to representatives for Trump in spring 2021 when they realized that important material from his time in office was missing from their collection.

According to the Presidential Records Act, White House documents are considered property of the U.S. government and must be preserved.

A Trump representative told the National Archives in December 2021 that presidential records had been found at Mar-a-Lago. In January 2022, the National Archives retrieved 15 boxes of documents from Mr. Trump’s Florida home, later telling Justice Department officials that they contained “a lot” of classified material.

That May, the FBI and Justice Department issued a subpoena for remaining classified documents in Mr. Trump’s possession. Investigators who went to visit the property weeks later to collect the records were given roughly three dozen documents and a sworn statement from Mr. Trump’s lawyers attesting that the requested information had been returned.

But that assertion turned out to be false. With a search warrant, federal officials returned to Mar-a-Lago in August 2022 and seized more than 33 boxes and containers totaling 11,000 documents from a storage room and an office, including 100 classified documents.

In all, roughly 300 documents with classification markings — including some at the top-secret level — have been recovered from Mr. Trump since he left office in January 2021.

HOW DID A SPECIAL COUNSEL GET INVOLVED?

Last year, Attorney General Garland picked a veteran war crimes prosecutor with a background in public corruption probes, Jack Smith, to lead investigations into the presence of classified documents at Mr. Trump’s Florida estate, as well as key aspects of a separate probe involving the January 6, 2021, riot and efforts to undo the 2020 election.

Mr. Smith’s appointment was a recognition by Mr. Garland of the politics involved in an investigation into a former president and current White House candidate. Mr. Garland himself was selected by President Biden, whom Mr. Trump is seeking to challenge for the White House in 2024.

Special counsels are appointed in cases in which the Justice Department perceives itself as having a conflict or where it’s deemed to be in the public interest to have someone outside the government come in and take responsibility for a matter.

According to the Code of Federal Regulations, a special counsel must have “a reputation for integrity and impartial decisionmaking,” as well as “an informed understanding of the criminal law and Department of Justice policies.”

DIDN’T MR. BIDEN AND VICE PRESIDENT PENCE HAVE CLASSIFIED DOCUMENTS, TOO?

After classified documents were found at Mr. Biden’s think tank and Mr. Pence’s Indiana home, their lawyers notified authorities and quickly arranged for them to be handed over. They also authorized other searches by federal authorities to search for additional documents.

There is no indication either was aware of the existence of the records before they were found, and no evidence has so far emerged that Messrs. Biden or Pence sought to conceal the discoveries. That’s important because the Justice Department historically looks for willfulness in deciding whether to bring criminal charges.

A special counsel was appointed earlier this year to probe how classified materials ended up at Biden’s Delaware home and former office. But even if the Justice Department were to find Mr. Biden’s case prosecutable on the evidence, its Office of Legal Counsel has concluded that a president is immune from prosecution during his time in office.

As for Mr. Pence, the Justice Department informed his legal team earlier this month that it would not be pursuing criminal charges against him over his handling of the documents.

DOES A FEDERAL INDICTMENT PREVENT MR. TRUMP FROM RUNNING FOR PRESIDENT?

No. Neither the indictment itself nor a conviction would prevent Mr. Trump from running for or winning the presidency in 2024.

And as the New York case showed, criminal charges have historically been a boon to his fundraising. The campaign announced that it had raised over $4 million in the 24 hours after that indictment became public, far smashing its previous record after the FBI search of Mr. Trump’s Mar-a-Lago club.

HOW ARE MR. TRUMP’S REPUBLICAN RIVALS REACTING TO THE NEWS?

Many of Mr. Trump’s challengers for the GOP nomination jumped to his defense Thursday night after news of the indictment broke.

Governor DeSantis, Mr. Trump’s top rival for the 2024 nomination, accused the Justice Department of political bias in charging the former president.

“The weaponization of federal law enforcement represents a mortal threat to a free society,” Mr. DeSantis tweeted. “We have for years witnessed an uneven application of the law depending upon political affiliation.”

He questioned why the Justice Department had been “so zealous” in bringing charges against Mr. Trump and “so passive” about going after a former Democratic presidential nominee, Senator Clinton, or Mr. Biden’s son Hunter.

Senator Scott of South Carolina said he felt the justice system’s “scales are weighted” based on politics. “In America, every single person is presumed innocent, not guilty,” Mr. Scott said on Fox News, decrying “the weaponization of the Department of Justice against the former president.”

Biotech entrepreneur and “anti-woke” activist Vivek Ramaswamy said the federal case was part of “an affront to every citizen.” Reiterating his comments that he would pardon Mr. Trump, Mr. Ramaswamy called it “hypocritical for the DOJ to selectively prosecute Trump but not” Mr. Biden over his own classified documents case.

Governor Hutchinson, who called for Mr. Trump to drop out of the race after the New York charges were filed, said the federal indictment marked “a sad day for our country” and “reaffirms the need for Donald Trump to respect the office and end his campaign.”

Mr. Pence said earlier Thursday that if Trump were to be indicted, he would hope the Justice Department had strong evidence — a shift in tone from the night before, when he said he hoped Mr. Trump wouldn’t be charged even if evidence is clear he committed a crime.

Associated Press