If Democrats gain enough power this election (both in President/Congress/State Levels) there are some things they can do to make sure Republicans never get back into this position of power again.
1. Strengthen and protect voting. Both ease of access and protection from interference from foreign and domestic entities.
2. Fix the gerrymandering at the state level. This will require more Dem governors and state legislators turn blue.
I am sure there are others. Please feel free to add