Shockwaves spread across America in response to the news that the FBI had searched the private Florida residence of Donald Trump, a dramatic and unprecedented move that prompted threats of retaliation from the former US president and his allies.

It also brought calls for accountability from his opponents and inspired speculation about what it could mean for Trump’s plans to run for the White House again in 2024, as some suggested it may prompt him to announce a candidacy before vital midterm elections in November.

The court-authorized raid on Trump’s Mar-a-Lago estate appeared to be related to a long-running investigation into whether he mishandled classified government documents when he left the White House in 2021.

In the hours after Trump announced on Monday evening that his “beautiful home, Mar-A-Lago in Palm Beach, Florida, is currently under siege, raided, and occupied by a large group of FBI agents”, top Republicans rallied to his defense, as America’s already divided politics roiled with reaction.

Kevin McCarthy, the House minority leader, threatened to investigate the justice department if his party wins control of the chamber next year, which forecasts suggest is probable.

“I’ve seen enough,” the California Republican wrote in a statement that he posted online. “The Department of Justice has reached an intolerable state of weaponized politicization.”

He went further, hinting that should he wield the gavel next year, House Republicans would open a congressional investigation into the attorney general, Merrick Garland. “Attorney General Garland, preserve your documents and clear your calendar,” he wrote.

Democrats, who have pushed the department to bring criminal charges against the former president for his role in the January 6 attack on the US Capitol, welcomed the raid.

“It is a horrible precedent for the Department of Justice to investigate a former president of the United States,” said congressman Ted Lieu, a Democrat from California who was a manager during Trump’s second impeachment trial. “The only worse precedent would be for @TheJusticeDept not to investigate because the person happens to be a former President. No one is above the law.”

Democrats also accused Republicans of hypocrisy after years of calling for the prosecution of Hillary Clinton, Trump’s 2016 Democratic rival in the presidential race, over questions of whether she mishandled classified information by using a private email server. Trump sought to exploit the investigation and encouraged chants of “lock her up” during campaign rallies.

Referring to McCarthy, Congressman Don Beyer, a Democrat from Virginia, said: “This man and his fellow bootlickers hid under a rock rather than respond every time Donald Trump called for persecution, investigation, imprisonment or violence against his political opponents.

“These same people talk about Trump like he’s above the law. He’s not above the law.”

The FBI’s presence at Mar-a-Lago in Palm Beach on Monday was reportedly related to its investigation into whether Trump unlawfully took classified documents from the White House to his Florida residence rather than turn them over to the National Archives. Some Democrats have gleefully pointed out that a possible, albeit unlikely, punishment for mishandling sensitive government documents is disqualification from holding future federal office.

What exactly federal investigators were looking for remains unclear. But to obtain the search warrant, investigators would have had to show a judge that they had probable cause of a crime and that there was relevant evidence located at Mar-a-Lago. Trump, who disclosed the search in a furious statement, said investigators had entered his home and opened a safe.

Given its unprecedented and political nature, legal experts speculated that investigators would probably have sought authorization from the highest levels of the justice department.

Many also noted that Trump would have been shown a copy of the warrant, but has chosen not to make that information public.

In an interview on Fox News on Monday night, Trump’s son, Eric Trump, said that the search happened because “the National Archives wanted to corroborate whether or not Donald Trump had any documents in his possession”.

Lashing out at the FBI, the younger Trump said he believed the raid was an attempt to prevent his father from running again in 2024.

“Honestly, I hope – and I’m saying this for the first time – I hope he goes out and beats these guys again because honestly, this country can’t survive this nonsense,” he said. “It can’t.”

Trump is widely believed to be pursuing a presidential run in 2024, and many speculated that the raid would benefit him politically. Some suggested that it would fuel his supporters’ suspicion of federal law enforcement officials, whom Trump and his allies have long disparaged as corrupt and biased and part of an anti-Trump conspiracy they call the “deep state” – although former aide Steve Bannon has dismissed the concept of the deep state. It also served to rally his allies and potential 2024 Republican rivals to his side.

Ron DeSantis, the Florida governor viewed as a possible contender in 2024, said the search of Trump’s beachside property was “another escalation in the weaponization of federal agencies against the Regime’s political opponents”.

Despite insinuations by Republicans that Biden was behind the raid, the White House said it was unaware of the search before it happened.

“The president and the White House learned about this FBI search from public reports,” the White House press secretary, Karine Jean-Pierre, said on Tuesday. “We did not have advance notice of this activity.” She added that as president, Biden vowed to restore the independence of the justice department after years of Trump’s efforts to pressure his attorneys general to advance his agenda.

The Florida search is far from the only legal trouble facing the former president, all of which he has cast as political witch-hunts.

The justice department is also investigating the January 6 riot and efforts to overturn the 2020 presidential election that Trump groundlessly claimed was stolen. It remains unclear whether Trump is a target of the inquiry.

In Georgia, a prosecutor in Atlanta is looking into a phone call Trump made to the state’s secretary of state in which he pressured him to “find” just enough votes to reverse Biden’s 2020 victory in the state. And in New York, the state attorney general, Letitia James, is leading an investigation into Trump’s family business.

In another blow, the DC circuit court of appeals ruled on Tuesday that the House ways and means committee can obtain Trump’s tax returns from the Internal Revenue Service, a decision the House speaker, Nancy Pelosi, hailed as a “victory for the rule of law”.

As news of the Mar-a-Lago search reverberated across the country, a crowd swelled outside Trump’s upmarket private resort club and residence, where supporters waved American flags and some showcased campaign signs with Mike Pence’s name crossed out.

Online, far-right Trump supporters raged against the FBI’s search of Mar-a-Lago. In the hours after the disclosure, references to “civil war” spiked on Twitter while Maga and QAnon forums lit up with violent rhetoric and threats of civil unrest, alarmingly similar, analysts and reporters said, to the kind of activity observed on these platforms in the lead-up to the January 6 insurrection. The top comment ​​on a pro-Trump message board was “Lock and load.”