Why impeachment, and why now?
The current impeachment is about one thing and one thing only. It is about Democrat incumbents in Congress winning future Democrat primaries.
I have thought since the 2018 election that this Congress would impeach President Trump. My original guess was that they would impeach President Trump in their lame duck period after the 2020 election, whether the Democrats or Republicans win a majority in the Congress in the 2020 election, whether or not the GOP retains control of the Senate, whether or not he wins re-election in 2020.
The lame duck session after the 2020 election is the safest time for Democrats to impeach President Trump. Whether President Trump has been re-elected or not, the Senate and President Trump's supporters will ignore the impeachment vote. That makes a lame duck Congress impeachment safe for Democrats.
Having voted to impeach President Trump will be a badge of honor in every Democrat primary for the next couple of decades or beyond. If you were a member of the 116th Congress and voted for the impeachment of President Trump, it will help you win Democrat primaries the next couple of decades. If you were a Democrat member of this Congress and never had a chance to vote on the impeachment of President Trump, the loudest part of the Democrat primary electorate will still blame you as part of the problem. This is because despite the Democrats having control of Congress, when you were there, you, the collective Democrat in the majority, did not impeach President Trump.
Thus, even if you are a Democrat member of Congress from a district that President Trump carried in 2016, you may still need to vote to impeach him to fend off primary challenges. If you are a Democrat member of Congress on record voting against the impeachment of President Trump, there may be no Democrat primary anywhere in the country you can win.
Even if you are a Democrat who is in a good shape for their 2020 primary, you may have your vote or lack of a vote on the impeachment of Trump crop up in 2022 or 2024 and beyond primary. You could become the next Joe Crowley and lose to an upstart in a low-turnout election, where only the hard core of your party turns out.
So why impeach now rather than, as originally thought, in the lame duck session, when you know whether or not President Trump has been re-elected or not? This well could be a sign that congressional Democrats are starting to worry about the monster they have created in their base. Having to explain not having voted to impeach yet before the 2020 Democrat primary may be worrying Democrat members of Congress.
Equally, GOP Senators do not want a vote on impeachment. They must vote to acquit, or they too face potential problems in future GOP primaries. Senators, of course, face primaries only one third as often as members of the House. That includes senators like Mitt Romney, Ben Sasse and even Susan Collins. For a GOP Senator whose voting record is somewhat out of step with constituents, impeachment will be an opportunity to shore up their base by voting against. Still, the GOP senators are an afterthought to the Democrats in Congress, and the Democrats in the Senate have no problem if the Congress never sends impeachment to them.
The bottom line is that all the talk about Ukraine, quid pro quo, the House rules, President Trump's tweets, obstruction, etc. is irrelevant to this impeachment process. Evidence does not matter. Whether an "offense" is impeachable or not does not matter. The House conducting its investigation in secret and locking out Republicans does not matter. This impeachment is all and only about the 2020, 2022, 2024, 2026, 2028, and beyond Democrat primaries.