And the reason for impeachment isn't to shave a few more points off of Trump's approval rating. I think serious investigations and hearings can do this, contrary to fears that we might make the MAGAs mad and then, um, something. But it isn't the point.
The point is to highlight all the things that are unacceptable in our too powerful executive and, to the extent that this Congress can, draw some lines.
As I've said repeatedly, "impeachment" wasn't the only way to do this, but failing to do it in other ways, combined with Barr's increasing suggestions that anything but impeachment (and soon even that) is just illegitimate behavior by Congress, made it more inevitable.
The man has spent years doing obvious crimes and bragging about them. Sternly worded tweets and pleas for Republican Daddies to save us were never going to be enough. Gotta use the power.
Limiting it to one thing and getting off the table as fast as possible isn't going to be enough.
Assuming there is no chance of the Republican Senate convicting Trump, and I still don’t think there is, an impeachment vote on one solitary scandal amounts to a vote of censure: a weightless illusion of accountability, and a chance for members of our political class to say that our system worked as intended when it really has not done so for some time now. Censure only humbles a person with respect for the system. Trump isn’t terrified of the prospect of an eternal asterisk in his Wikipedia entry labeled “impeached.” He’s terrified that people will actually find out every rotten thing he and his kids have been up to.