The alternative to the following, addressing your skepticism, would be that a POTUS who engages in political crimes cannot be held accountable by congress if the offenses he commits occur late in his term. Trump has now been impeached twice for abuses of office of the same motive, misusing his office for the political purpose of staying in the office regardless of the vote result or on an even playing field compared to his opponent. IOW, Biden lacked the leverage of a $400 million miltary aid shakedown after announcing to the world Putin was trusted over U.S. Intel agencies contrary findings, formidable leverage against the new President of Ukraine to do Trump's bidding. It is an absurd argument that is opposite a statute of limitations to claim a political accountability trial cannot occur after the expiration of the accused office holder's term in office!
The Senate has conducted past trials after officials have resigned or left office
"...The text of the Constitution’s pardon clauses does not directly address late impeachability.
Article II, Section 4 states: “The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.” On its face, this says only that officeholders are removed if in office when convicted;
it does not say that an official must still be in office at the time of his or her impeachment and conviction. Congress has used this clause to limit impeachment to people who were officers at the time they committed their offenses, not to people who were officers at the time of their trial.
....
....The first impeachment trial under the new Constitution, in 1798, was of an ex-official: Sen. William Blount had conspired to give the British control over then-Spanish Florida and parts of French Louisiana. As soon as the plot was exposed, the House impeached him. The Senate expelled him soon after. At his impeachment trial, Blount’s lawyers argued Blount could not be tried because he was no longer a senator. That argument failed. Blount was ultimately acquitted by a vote of
14-11, but on the basis that senators are not “officers” subject to impeachment in the first place.
An even stronger precedent is the 1876 case of ex-secretary of war William Belknap. After his corrupt scheme to sell a post as Indian agent was revealed to the House, Belknap quickly resigned before he could be impeached. But the House impeached the “late Secretary of War” anyway. The Senate debated late impeachability for over a month before voting 37-29 that it had the power to try an ex-officer. Belknap was nonetheless narrowly acquitted. Based on senators’ statements, there probably would have been enough votes to convict Belknap if he had not already left office. But the Senate did decide it had jurisdiction — in the end, it determined only that Belknap shouldn’t be convicted, not that he couldn’t be..."
