Attempted impeachments, even when successful, have so far had ZERO chance of removing the targeted President from office, without his consent. Almost always, the fallout has damaged the party that tried to remove the target much more than the party that defended the President involved.
Impeachment is a fool’s errand on the best of days, even against an otherwise unpopular President.
Nobody is so much of an underdog that there are no defenders taking his part.
That and the rest of your post is spot on - at least as it applies to traditional impeachment. However, there is a chance the Socialist Dems do not intend to conduct a successful impeachment (they have little to lose, they know they probably won't beat him straight up).
Rather, they may only intend to consider a series of "bombshell" allegations designed to provide 24/7 negative press in the months leading up to the primaries. Such would certainly include grave concerns expressed by Senate Dems about necessity of a trial prior to the presidential election. The objective, of course, will be to produce just enough doubt in the minds of R voters to defeat him at the primary level.
(See the groundbreaking "Ballsy" Ford epic in this regard.)