Why Do People Vote Democratic?

In a recent survey, 15% of republicans admitted to wishing mass death on fellow Americans who don't vote like they do. 20 % of democrats owned up to occasionally wishing mass death in the same way. How did we get here? That is a complicated story with more debate than consensus in the political science literature. What is clear though is that a lot of it was more by accident than by design. Some of what has happened over the past 20 years to increase polarization and political hatred is just the by product of consumer choice.