President Biden, facing a special counsel investigation amid new revelations of classified documents in his possession after the vice presidency, suddenly confronts a ballooning political problem that threatens to hamstring his agenda and blunt the momentum he hoped to seize at the halfway mark of his term.

Congressional Republicans, who just days ago were displaying bitter discord and nearly coming to fisticuffs on the House floor, are now launching new investigations and inquiries. Attorney General Merrick Garland announced Thursday he was appointing a special counsel in the deepening probe, which could mean interviews, searches of additional Biden properties and potentially weeks of headlines.

More immediately, Biden’s possession of classified documents is likely to rob him of the unvarnished ability to criticize former president Donald Trump for his own handling of sensitive material — even if the cases, and the two presidents’ approach to them, have been notably different.

The unexpected focus on the classified documents comes at a moment when Biden and his aides had been buoyant over midterm election results that were far better for Democrats than they feared. Biden seemed to revel in the Republican infighting on full display last week when it took 15 ballots before Rep. Kevin McCarthy (R-Calif.) was elected House speaker. And the president is widely expected to announce his reelection bid in the coming months, as his approval ratings rise and the economy is on firmer ground.

The potential peril was on vivid display Thursday morning when Biden held an event to tout the good economic news that inflation was down and conditions for consumers were improving. Just before he took the stage, Biden’s lawyers revealed that a second batch of classified documents had been discovered in two separate areas of the president’s home in Wilmington, Del.

As soon as he finished talking, reporters shouted questions — not about the improving economy, but about why documents were found in his garage next to his prized 1967 Corvette Stingray.

“My Corvette is in a locked garage, okay? So, it’s not like they’re sitting out in the street,” Biden responded. “But as I said earlier this week, people know I take classified documents and classified material seriously. I also said we’re cooperating fully and completely with the Justice Department’s review.”

Biden promised to provide more information before long. “I’m going to get a chance to speak on all this, God willing, soon,” he said.

But about two hours later, Garland announced the appointment of special counsel Robert Hur to look into his possession of the documents, a decision that could limit Biden’s ability to speak publicly.

For Democrats traumatized by Hillary Clinton’s 2016 struggle to justify the handling of her own records — with some blaming the media for giving the story outsize influence — Thursday’s furor provided an uncomfortable hint of what might lie ahead, while threatening to muddy Democrats’ criticism of Trump for taking larger numbers of sensitive documents to his home in Mar-a-Lago.

“I don’t think Biden has legal worries here, I don’t think he has political worries,” said Brian Fallon, a former Clinton adviser who worked at the Department of Justice. “The main benefit [for Republicans] is Trump is breathing a sigh of relief because it makes it hard for Merrick Garland to authorize a prosecution of Donald Trump, even if it is merited.”

Biden last fall was shown a photo of top secret documents laid out on the floor at Mar-a-Lago, Trump’s estate in Palm Beach, Fla. Biden voiced disbelief during an interview with CBS News’ “60 Minutes” about how something like that could happen — how anyone, in his words, “could be that irresponsible.”

It was two months after that, on Nov. 2, that his lawyers discovered a small batch of classified documents in one of Biden’s offices in Washington, a discovery that Biden said earlier this week “surprised” him. On Thursday, Biden and his lawyers disclosed that the second batch of classified documents was discovered in the president’s home in Wilmington.

The revelations, dribbling out throughout the week, began to reveal a picture whose legal significance is still murky but whose political ramifications seem clearer. For one thing, the flap could get at some of the self-proclaimed strengths — experience, competence and familiarity with the workings of national security — of a president who has often stressed how seriously he takes the country’s intelligence and diplomatic traditions.

In addition, there is now a special counsel scrutinizing Biden, Hur, as well as the one investigating Trump, Jack Smith. That creates at least a superficial equivalence between the cases — one that triggered some Democratic criticism of Garland on Thursday — with Republicans likely to complain of a double standard if Biden faces fewer consequences.

Biden’s aides have gone to great lengths to point out how their behavior differed from Trump’s. The former president apparently knew what he was taking and declined to give them back, while Biden says he did not even realize he had any classified papers and turned them over as soon as they were discovered.

Biden’s allies echoed that point Thursday.

“Well, I think a lot goes toward intent … Was this something that was unintended or intended?” said Rep. Bennie G. Thompson (D-Miss.). He added, “If I find it, and I said, ‘Look … for whatever reason, it didn’t get returned. We found it here and here.’ I don’t see any deception with that. Whereas obviously there was some deception associated with the Mar-a-Lago.”

But the White House has done less to explain how the documents ended up in Biden’s office and home in the first place.

At Thursday’s White House news briefing, press secretary Karine Jean-Pierre repeatedly rebuffed questions about the documents, citing the ongoing investigation and saying that the administration is “trying to do this by the book.”

“The president takes this very seriously,” Jean-Pierre added. “He was not aware that the records were there. He does not know what is in the documents.”

She declined to answer questions about whether Biden would be willing to be interviewed by investigators; how and why the documents were taken to his office and home; who had access to the rooms where classified documents were found; and why the White House did not initially reveal that a second batch of documents had been discovered.

Republicans said the revelations raised serious questions about Biden’s actions, and they almost immediately began making requests, drafting letters and pledging investigations.

Rep. Michael R. Turner (R-Ohio), incoming chairman of the House Intelligence Committee, requested briefings by Jan. 26 from Garland and Avril Haines, the director of national intelligence.

“The presence of classified information at these separate locations could implicate President Joe Biden in the mishandling, potential misuse, and exposure of classified information,” Turner wrote in the letter. “It raises significant questions as to why then-Vice President Biden maintained custody of such highly classified documents, who had access to them, and for what purposes.”

Rep. James Comer (R-Ky.), chairman of the House Committee on Oversight and Accountability, said his committee would also investigate.

“There are many questions about why the Biden administration kept this matter a secret from the public, who had access to the office and the residence, and what information is contained in these classified documents,” Comer said.

Rep. Jim Jordan (R-Ohio) suggested the Biden documents would also be one of the priorities of the GOP’s newly created committee on the ostensible weaponization of the government.

As for Trump, in a post to his Truth Social network, he called on Garland to end Smith’s investigation of his activities and “appoint a special counsel to investigate Joe Biden who hates Biden as much as Jack Smith hates me.”

The Trump campaign has been pleased with the coverage of the Biden documents, an adviser said, with Trump posting several cable news clips on Truth Social. “Are they going to raid the White House?” Rep. Max L. Miller (R-Ohio), a former Trump aide, said in one of the clips, from Newsmax. “Are they going to go after President Biden with the same vigor?”

Other right-wing websites chimed in with headlines calling for Biden’s impeachment and criticizing media reports pointing out the differences between Trump’s and Biden’s circumstances.

Much of the coverage on the right has argued that Biden’s actions were worse because he was a former vice president rather than a former president. But the Presidential Records Act treats vice-presidential records the same, and the vice president has equivalent declassification authority (though Biden, unlike Trump, has not cited that authority as justification for keeping the documents).

Republicans may face their own conundrum regarding the documents, given the parallel investigations of the two presidents. If they accuse Biden of acting egregiously, that could weaken any assertion that Trump acted responsibly. And if they defend Trump’s behavior as harmless, it may be harder for them to argue that Biden is guilty of a major transgression.

But a wide variety of documents can be marked as classified, and the ultimate political fallout for Biden could depend in part on the nature of the papers found at his home and office. The documents at Trump’s residence included highly sensitive material on China and Iran, The Washington Post previously reported.

Matthew Miller, a Justice Department spokesman in the Obama administration, argued that whatever the immediate embarrassment for the White House, the contrast with Trump will eventually work to Biden’s advantage.

“I think they’ll have a very clear case to say the president handled this prudently — and the former president refused to turn over documents, misled investigators and then forced the FBI to raid his house,” Miller said. “In the short term, it’s a very uncomfortable issue for the White House. But in the long term, it could play pretty favorably for them.”

The special counsels, meanwhile, will make charging decisions that will have a far greater impact than the political messaging, Miller added. “One of the things about the politics of Trump — it’s determined by whether he gets indicted or not,” Miller said. “It almost matters less what Biden will say about it than what’s actually playing out in the legal process.”

Rep. David Joyce (R-Ohio) said the fact that both Trump and Biden are facing problems over their handling of classified documents suggests a bigger issue for the nation.

“In either situation, those documents should be in a secure facility,” Joyce said, adding, “You’re in the same boat that Trump is in now. Let’s find out why these documents aren’t making it to secure facilities.”

Isaac Arnsdorf contributed to this report.