At the end of the day, whether or not you voted for Trump in '16 in the general, or consider your self a Never Trumper, who are you going to vote for in 2020?? I think Trump will remain unopposed and certainly if not, who ever opposes him will lose.
Not many options as it doesn't seem that there will be a worthwhile 3rd party who will have qualified in all 50 states, which leaves the choice between Trump or a DEM. Personally, I can't think of any DEM that is worthy of my vote.
I have seriously considered just voting down ballot, but that doesn't accomplish my primary objective of stopping the left. On the other hand Trump's failure on the border is very troubling and I am not convinced that he never intended to secure the border or build a wall.