He could be Impeached. "At the federal level, Article II of the United States Constitution states in Section 4 that "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." https://en.wikipedia.org/wiki/Impeachme ... ted_States
It seems to be a complicated process, and has to be initiated by the House of Representatives, it seems. "Two U.S. Presidents have been impeached by the House of Representatives—Andrew Johnson in 1868 and Bill Clinton in 1998—both later acquitted at trials held by the Senate. ... When an impeachment process involves a U.S. President, the Chief Justice of the United States is required to preside during the Senate trial."
The specific grounds seem to be “treason, bribery, and other high crimes and misdemeanors”, which need clarification. http://www.crf-usa.org/impeachment/high ... anors.html
The Republicans have a majority in both Houses, but these days, with the situation there ( and here) seeming to change almost daily, who knows where we will be in a couple of weeks?
ETA. There is also the 25th Amendment.
https://www.washingtonpost.com/opinions ... story.html
There is, however, another way. Under the 25th Amendment to the Constitution, the vice president, together with a “majority of either the principal officers of the executive departments or of such other body as Congress may by law provide” can remove the president for being “unable to discharge the powers and duties of his office.” No doubt the mere mention of incapacitation would summon a horde of lawyers to Washington to contest it or the meaning of every term.