I thought I might add that not only do I not believe that gerrymandering is responsible for political polarization, I don’t even think gerrymandering has played a large role in making House seats uncompetitive. For any given district and any given incumbent, there’s some set of ideological properties in a challenger that should be winnable. To think of it in a stripped-down way, any district, no matter how gerrymandered, has a median voter and a sufficiently motivated challenger can make a good shot at finding him.
The real issue, I think, is the relative scarcity of campaign funds. If every major party nominee in every House district in America were guaranteed a reasonable sum of public funds with which to conduct his campaign then I think you’d suddenly see all sorts of interesting candidates popping up in “uncompetitive” districts. This, of course, is precisely why incumbent legislators would be loathe to vote for such a public financing scheme. But that’s the real issue.