William Howard Taft, the 27th US president, had choice words for describing what should become of former occupants of the White House once they left office.

“A dose of chloroform”, Mr Taft reportedly said — to protect the nation “from the troublesome fear” they would ever return.

Mr Taft — who went on to become a Supreme Court justice — was thinking not of himself, presumably, but of his White House predecessor and former ally Theodore Roosevelt. At the end of Taft’s first term, Roosevelt challenged him first for the Republican nomination and then the presidency; both men ultimately ended up losing to Woodrow Wilson.

It is hard not to think of Taft’s advice when contemplating the future of Donald Trump. Though he must leave the White House next week, he has done nothing to suggest — even after he was blamed for last week’s riot — that he will retreat from the public sphere.

At the “save America march” last Wednesday that morphed into a siege of the Capitol, Mr Trump, his family and remaining top aides appeared not to be looking back on his four-year White House term, but ahead to the next phase of a movement that has splintered the Republican party and rattled American democracy.

A video posted by the president’s eldest son, Donald Trump Jr, last week showed members of the president’s inner circle dancing backstage to the 1982 pop hit “Gloria” ahead of the event, as if it were just another campaign rally. Mr Trump and his advisers have repeatedly hinted at another run in 2024. But he now faces a significantly more challenging path. The House of Representatives is moving towards the second impeachment proceedings against him in a year.

A raft of potentially devastating legal challenges await him as the former president. Both federal and local prosecutors in New York are already investigating him, and there are calls for probes of his phone call asking Georgia’s secretary of state to “find” votes for him, as well as his role in the January 6 violence.

A small but growing number of Republican lawmakers have called on the president to resign or be impeached. Twitter has permanently suspended Mr Trump’s account, cutting the president off from his 88m followers.

It would be naive to write off Mr Trump’s political prospects or to assume that he has lost the bulk of his devoted fan base. Yet he will be rallying them from a diminished pulpit, and not just because of his shuttered social media accounts.

“There is no way Donald Trump realises how overnight you go from being the most powerful human on the planet to becoming a nobody,” Douglas Brinkley, the presidential historian, notes.

“You think: ‘I’m a big celebrity and I have followers and I’ll come back in 2024. But now you’re fighting with no official power around you. None. Even ones that don’t have big egos, like Jimmy Carter and George H W Bush, have a hard time adjusting to [civilian] life.”

The elder Bush dipped back into White House politics after his defeat, following the election of his son, whom he would occasionally join for the classified President’s Daily Brief on his visits back to Washington.

Mr Carter, meanwhile, was at times criticised for meddling too much in the affairs of his successors, such as when he was seen to be interfering with Bill Clinton’s policies towards North Korea, and the elder Bush’s with regards to Kuwait.

For some ex-presidents who left on less than ideal terms, the post-presidential period has offered a chance at redemption, financial or otherwise. But the PGA has just stripped Mr Trump’s Bedminster golf course of a major 2022 tournament and his hotels business may face broader fallout.

Furthermore, the most content ex-president right now appears to be George W Bush, who moved back to Texas and happily took up painting.

If Mr Trump does push ahead with another White House run, he will not be the first former office-holder to do so. Martin Van Buren, Millard Fillmore, Ulysses S Grant, Grover Cleveland, Herbert Hoover and Roosevelt all tried to recapture the White House after leaving office. Only one — Cleveland — succeeded.