WASHINGTON >> As a businessman and president, Donald Trump faced a litany of lawsuits and criminal investigations yet emerged from the legal scrutiny time and again with his public and political standing largely intact.

But he’s perhaps never confronted a probe as perilous as the Mar-a-Lago investigation, an inquiry focused on the potential mishandling of top-secret documents. The sense of vulnerability has been heightened in recent weeks not only by the Justice Department’s appointment of a special counsel with a reputation for aggressiveness but also by the removal of a Trump-requested independent arbiter in the case and by judges’ unequivocal rejection of his lawyers’ arguments.

It’s impossible to predict how much longer the investigation will last or whether the Justice Department will take the unprecedented step of indicting a former president and current candidate. But Trump is no longer shielded from prosecution the way he was as president, and some legal experts regard the Mar-a-Lago investigation as centered on more straightforward factual and legal questions than the prior probes he has dealt with.

“Unlike many of these past investigations which involved these complex financial frauds where prosecutors have to explain to a jury why the conduct is even a crime to begin with, here prosecutors won’t have that difficulty, won’t have that challenge to explain what the crime is about” if charges are ultimately filed, said former Justice Department prosecutor Robert Mintz.

One investigative hurdle for the Justice Department was lifted last week when an appeals court panel that included two Trump-appointed judges ended the work of a special master who’d been tasked with an independent review of the thousands of documents seized in the FBI’s search of Mar-a-Lago. The decision enables prosecutors to use the entire cache of records for their investigation.

In a scorching opinion that reached deep back into history, the court acknowledged that a search of an ex-president’s property is extraordinary but not so extraordinary as to afford him special treatment.

“It’s not often you see cases cited in a court of appeals decisions that were decided in 1794, in the 1800s,” said David Weinstein, a Florida criminal defense lawyer and former federal prosecutor. “These are bedrock principles of law that have long existed that they relied on.”

Of course, investigations are nothing new for Trump, and speculation about his legal jeopardy has been off-course before.

Last year, state prosecutors in New York indicted Trump’s business, the Trump Organization, and its longtime chief financial officer — but did not charge the former president. In September, the New York attorney general accused Trump of padding his net worth by billions of dollars and misleading banks — but those allegations were made in a lawsuit, not a criminal case.

As president, he was investigated by an earlier special counsel, former FBI Director Robert Mueller, over whether his successful 2016 campaign had illegally colluded with Russia and whether he had tried to obstruct that probe. Mueller ultimately found insufficient evidence to allege a criminal conspiracy between the campaign and Russia and also cited longstanding Justice Department policy that prohibits the indictment of a sitting president.

The obstruction prong of that investigation involved an analysis of constitutional law and the scope of presidential power. But prosecutors in the Mar-a-Lago probe have largely dismissed the relevance of Trump’s status as a former president, asserting during a court fight over the special master that the classified records he had access to as commander-in-chief don’t still belong to him.

And the appeals panel in its opinion last week rejected the idea that Trump was entitled to the return of the records seized from his home or to have an independent arbiter go through them, something it said would create a “special exception.”

The records investigation had simmered for months before bursting into view with an Aug. 8 FBI search of Mar-a-Lago, with agents removing roughly 100 documents with classification markings. By that point, Justice Department officials say they’d developed probable cause to believe crimes had been committed related to the retention of national defense information as well as obstruction.

The investigation has since shown signs of accelerating, with the Justice Department presenting evidence before a grand jury and granting immunity last month to a Trump ally to secure his testimony.

The probe is being run by Jack Smith, who previously led the Justice Department’s public integrity section and more recently has served as a war crimes prosecutor in the Hague. Smith is also overseeing key aspects of a separate Justice Department investigation related to efforts by Trump and his allies to undo the results of the 2020 presidential election. The Fulton County, Georgia, district attorney is separately investigating attempts to overturn that state’s results too.

Smith’s appointment by Attorney General Merrick Garland came three days after Trump declared his White House candidacy. The announcement won’t stop the investigation, though it may quicken the pace so as to avoid colliding with the heart of the 2024 presidential race.

His candidacy could theoretically infuse the investigation with greater import, said former federal prosecutor Franklin Monsour Jr., since it will no longer be just about a former president. “It’s now about someone trying to become president again, and trying to possess national security material again.”

Yet, legal experts expect the Justice Department to weigh more than just the strength of evidence in deciding whether to proceed with a case. There will be questions over how much classified evidence it can present to a jury — and the feasibility of picking an impartial jury given Trump’s ubiquitous name recognition and the impassioned reactions he produces on both sides.

A prosecution of a former president also risks being seen as political, further polarizing an already divided country, as well as transforming a court into a circus-like atmosphere.

“It’s basically weighing the principle that no individual is above the law against the practical political fallout that bringing these kinds of charges against a former president, particularly one who is once again running for president, will engender,” Mintz said.

“It’s an extraordinarily difficult decision,” he added.