With gerrymandering - especially racial gerrymandering to insure black congressional districts - the Dems become increasing reliant on their safe seats in uban areas, the coasts, and small, isolated Dem islands in the rest of the country.
Thus, except for unusual election years (like this one seems to be), few seats are ever really contested. Congressional seats, like state legislative seats, tend to be sinecures.
The irony is that those "safe seats" and guaranteed black seats that the Dems wanted ended up creating Conservative seats also, by concentrating their voters in specific areas. Dem plantations, as it were - regardless of skin color.
Only in major "wave" elections are very many national seats contested. It's too rare. Every election should be contested or contestable. Safe seats cause us to end up with elderly lunatics like Barney Frank and John Conyers in charge of things - people who wouldn't be voted out even if caught running gay prostitution rings out of their houses.
This is one reason the national Dems become an increasingly Lefty party. It's a shame, because it would be the best for the country for no congressional seat to be taken for granted. I am a believer in the big tent approach for both parties. Debate and disagreement is good for all.
See this:
After midterms, House Democratic Caucus to become more liberal as House becomes more conservative
