Impeaching Trump now = conceding the 2020 election.
That's my working theory. I don't know if the Democrats in Congress will go so far as to impeach Trump, but I tend to think that if they do, it will be because they think they're going to lose the election and they need another route toward defeating Trump. Of course, if Trump is impeached by the Democrats who have a majority in the House, he will not be removed from office, because the Republicans control the Senate. We'll be subjected to a horrific blend of legal mystification and political advantage seeking. So why would the Democrats predict that it will advantage them? My answer is: because they feel sure they're losing the actual election, the straightforward political fight. The timing is important. They could wait for the actual election, the normal process of American democracy, or — if they think that won't work — they can start delegitimatizing it now, while they think they have a decent shot at making us believe they're doing something righteous