Donald Trump boarded Air Force One for the last time on Wednesday with a wave. As Frank Sinatra's My Way blared over the loudspeakers at Joint Base Andrews, the soon-to-be-ex-president took off for his new home in Florida. Although he had just finished promising a small gathering of supporters that he would be back "in some form", the future for Trump - and the political movement he rode to victory in 2016 - is murky. Just two months ago, he seemed poised to be a powerful force in American politics even after his November defeat. He was still beloved by Republicans, feared and respected by the party's politicians and viewed positively by nearly half of Americans, according to public opinion surveys. Then Trump spent two months trafficking in unsubstantiated allegations of electoral fraud, feuded with party officials in battleground states, unsuccessfully campaigned for two Republican incumbent senators in Georgia's run-off elections and instigated a crowd of supporters that would turn into a mob that attacked the US Capitol. He's been impeached (again) by a bipartisan vote in the House of Representatives and could, if convicted in the Senate, be permanently banned from running for public office. Over his five-year career in politics, Trump has wriggled free from political predicaments that would sink most others. He has been declared dead more times than Freddy Krueger. Yet he always seemed unsinkable; a submarine in a world of rowing boats. Until now. Stripped of his presidential powers and silenced by social media, he faces daunting challenges, both legal and financial. Can he still plot a successful political comeback? Will a Mar-a-Lago exile be his Elba or St Helena? And who might the tens of millions of Americans who supported him turn to instead?