When the president's actions (or inactions) provide "Aid and Comfort" to enemies or levy war against the United States, then Congress has the power to impeach and remove (convict) the president for treason.
A simple majority of the House is necessary to approve articles of impeachment. If the Senate, by vote of a two-thirds majority, convicts the official on any article of impeachment, the result is removal from office and, at the Senate's discretion, disqualification from holding future office.
Only three presidents—Andrew Johnson (1868), Bill Clinton (1998), and Donald Trump (twice, in 2019 and 2021)—have been impeached. Neither Johnson nor Clinton were convicted, and Trump’s first impeachment resulted in an acquittal by the Senate. One president, Richard Nixon, resigned his office in 1974 when it became clear that he would be impeached by the House and likely convicted by the Senate. Nixon was pardoned for his alleged misconduct by his successor, Gerald Ford.
President Trump’s recent forays into the details of military justice and other military disciplinary actions is a potentially dangerous deviation from this longstanding practice. Beginning on the 2016 campaign trail, candidate Trump denigrated the military justice system when he lambasted the financial resources wasted to court-martial Sergeant Bowe Bergdahl, a soldier pending general court-martial for several UCMJ violations resulting from his decision to abandon his combat outpost in Afghanistan. Instead Trump called for his execution as a traitor.
Only three presidents—Andrew Johnson (1868), Bill Clinton (1998), and Donald Trump (twice, in 2019 and 2021)—have been impeached. Neither Johnson nor Clinton were convicted, and Trump’s first impeachment resulted in an acquittal by the Senate. One president, Richard Nixon, resigned his office in 1974 when it became clear that he would be impeached by the House and likely convicted by the Senate. Nixon was pardoned for his alleged misconduct by his successor, Gerald Ford.
Would think it'd be a good idea to have an Acting POTUS Pence in place to pardon Trump should any efforts against him had been successful...
Great Read:
u/MAGAdeburger
u/CHAOSACTUAL
https://www.acslaw.org/expertforum/presidential-power-and-military-justice-a-tradition-of-effectiveness-under-strain/