Agreed with all. The closest we've had is the Clinton Impeachment [1], which of course didn't have a snowball's chance in hell of getting past a US Senate that would have required 13 Democratic defections, and in fact OTL not only had zero Democrats join with the Vast Right Wing Conspiracy [SIZE=-4]tm[/SIZE], but also had five Republican defections to Clinton!
1] I don't count the Johnson Impeachment, as A. Johnson was only months away from leaving office and the Impeachment was nothing more than an act of spite by the Radical Republicans.
IF the US Congress actually impeached and convicted a sitting President, it would have to happen under circumstances where:
a) The President still had a considerable amout of time left in office
b) The party in opposition had overwhelming majorities in both Houses of Congress (esp. the Senate; Lotsa Luck!)
c) The President is incredibly unpopular nationwide
d) The impeachment charges have to be more serious than the trumpery nature of previous attempts (Nixon level impeachment, IOW)
Remember this however: The then House Speaker Newt Gingrich speculated on TV the likelihood that Clinton would be Impeached and Removed, and then Gore would pardon Clinton, allowing the Congress to Impeach and Remove Gore. Thereby allowing Speaker Gingrich to assume the mantle of President of the United States!
The fact is these Gingrichian statements were used to help expose the true motives for the VRWC [SIZE=-4]tm[/SIZE] regarding impeaching Clinton. The idea that the Republicans could remove Clinton, including getting Democratic support for it [2], never seemed to waver in GOP minds at the time.
2] Does the Dark Side of the Force have the Jedi Mind Trick?