Now There's Proof: Gerrymandering is Bad
A large scale statistical analysis finds that artificially protecting incumbents through gerrymandering leads to weaker challengers of either party. The research finds that for both congressional and state legislative districts:
" A party disadvantaged by gerrymandering fails to contest more districts. The candidates it does nominate have weaker credentials. Donors give less money to these candidates. And voters are less inclined to support them. "
It is possible that the Supreme Court will take evidence such as this into account when considering challenges to gerrymandered districts.