Actually.... and I stated this before... I am not a Trump fan... there are policies I like and others I dislike from his administration. My primary problems with him is his excessive narcissism, sub-standard world understanding, and his communication style.
Many times I hope the Democratic party can find a middle-of-the-road, intelligent challenger for 2020 but I don't see this happening at the moment -- most of the proposed candidates lean strongly to the left (which makes them un-electable in the general election).
The reality -- at the moment -- is that I don't see any road to taking Trump out of office in 2020. Sitting presidents have significant election advantages and it is likely he will stay in office. If Trump gets impeached or charged than I will re-evaluate his chances. -- but for now I assume he will be in office for 8 years.