Typical Dem voting strongholds are overwhelming split 70-30 between Dems and Republicans. So they win these in landslides BUT their interparty fights mean that the most radical candidates prevail and push the party further and further toward the extremes. They try to compensate by siphoning off as many of their huge majority into districts that are closer to 50-50 so they can win more seats. The result has been that Republicans won far less seats in Democratic states than the % of their voters who lived there. However, the Republicans are now playing the same game (but are not doing it along racial lines... because THAT is unconstitutional). Regardless, this means that our politics has moved away from the center for both parties. Bottom line: gerrymandering it causing a huge political divide in this country that gets wider by the day.