Advantage, GOP Why Democrats have to win large majorities in order to govern while Republicans don’t need majorities at all https://fivethirtyeight.com/features/advantage-gop/ An in-depth article by 538 - go to link to read.
The only way Dems end most of this is by making DC and The US territories states than ending gerrymandering through federal law.Shame on Obama not doing this when he had the chance.