A few details:
Technically, the House Judiciary Committee had already announced that their investigations related to the Mueller Report material had an eye towards possible impeachment, so this isn't that big of a procedural leap. The major difference is that Pelosi et al. are pushing the Ukraine affair a lot harder.
KleinerKiller wrote: this finally makes Trump the third U.S. president ever to enter official impeachment proceedings (after committing countless impeachable offenses since entering office, but hey, the rules only matter sometimes).
Fourth. Andrew Johnson, Nixon, and Clinton all got this far. Nixon resigned while the Articles of Impeachment were being hammered out, but the investigation had very much been underway.
KleinerKiller wrote:I'm under no illusion that McConnell will allow the procedure to move past the Senate, but this is a huge black mark on the administration visible for all to see, and hopefully it will get dragged out well into the election year.
This isn't something that McConnell can just block at the procedural level. The Constitution requires that the Senate hear the case and vote on removal if the House votes to impeach. I don't think there's much chance that the vote would be successful, but it's not because the GOP caucus is that afraid of Mitch; they're afraid of getting primaried by a Trump supporter.
The good news for Democrats is that this puts several potentially vulnerable senators, perhaps even the Turtle King himself, in a bind. On one hand, they can vote for removal and feel the wrath of Trump supporters in their next primary, and on the other hand they can vote to acquit and risk losing support in the general election if the public thinks he's guilty.
And of course, whether the Senate GOP manages to find their conscience or not, I think it's important in the long run for Democrats to take a stand for government accountability. Sooner or later the electorate is going to get sick of Trumpist chaos, and when the backlash comes it will benefit the Dems to be the party of responsibility.