and to add further a twofold problem for the democrats:
1.senate impeachment hearings are required attendance.
which means that the democratic candidates who are senators will have to attend.this can be as many as 5 to 6 days a week.stripping them of vital and valuable time to campaign.
2.there is no way that the democrats will get 2/3rds of the votes needed in the senate (or 20 republican votes if want to be precise).which means that not only will trump avoid impeachment,but he will be vindicated and triumphant.allowing him free press to do a country wide victory lap.
conclusion:
the democrats have essentially shot themselves in the foot and handed trump the 2020 election,and may have possibly nuked their own party.