“The problem, as reformers see it: Partisan gerrymandering has led to Congressional districts in which one party is so dominant that whichever candidate they nominate will win in November. About three-quarters of all districts, according to some estimates, are so overwhelmingly Republican or Democratic that the other party doesn’t have the slightest hope. So candidates from the dominant party have an incentive to align themselves with the partisan base that will turn out in a primary. Only hard-core partisans vote in a primary, meaning those candidates are playing to the extremes of either party — Republicans try to be the most conservative candidate in the field in deep-red districts, while Democrats try to be the most liberal candidate in sky-blue districts. The districts are drawn in such a way that there aren’t enough independents and voters of the minority party to punish extremism on either side.”