American elections

Democrat prospects rising steadily for the US congressional elections (which has downside of providing an incentive for invasion of Iran). Some works such as Off Center argue that gerrymandering, low turnout and political polarisation has made fewer and fewer congressional seats marginal. But if the Republicans are drawing boundaries to create more Republican seats this means that they are spreading their vote more thinly. When a party does poorly partisan gerrymanders are counter-productive as they reduce the number of safe seats. Electoral manipulation in Australia has not been gerrymandering but rather zonal systems that inflate the value of votes. I can't see why a swing against the Republicans should be restricted to Democrat held seats. Thus election looks encouraging. However Senate is more difficult as here there is a pro-Republican 'zonal' bias: two senators each for Wyoming and California.