I don’t have anything interesting to say about this, but commenters might like a space for a discussion, so here it is.
As a peg, let me suggest the very practical question whether House Democrats should pursue a broad or a narrow investigation, within the bounds of “high crimes and misdemeanours” not bad policies as on immigration and trade.
For narrow: the record of the Ukraine phone call conclusively proves abuse of office; no serious defence possible; gets it over with quickly.
For broad: impeachment will in any case not lead to removal; the object is to educate the electorate about the unfitness of not only Trump but most of his Cabinet and his enablers in the Senate, so lay out all the dirt; the open-and-shut Ukraine count will help shake loose evidence on other offences like money laundering for Russian mobsters.
There are nuances within the broad approach. Take violation of the oath of office to “faithfully execute the laws.” Trump and his minions have instead done their worst to sabotage both ACA and the Clean Air Act. Very dirty pool, but I suspect most voters will treat these as policy choices (maybe very bad ones) not potential abuses of power. There is quite enough to go on without taking this risk.
PS: “Perhaps the horse will learn to sing”. McConnell is a thug, but his own thug not Trump’s. There are circumstances – very unlikely but not impossible – in which Mitch would conclude that Trump is a net liability to the Congressional GOP. We may reasonably question if VP Pence has the cojones to stick the knife in if necessary. There is no such doubt about McConnell.
PS2: If any of my fellow-bloggers chimes in with something more substantial, commenters please shift the discussion to that thread.