Perpetually increasing polarization means that fewer states are competitive, there is less ticket-splitting, and candidate effects are weaker.

Perpetually increasing polarization means that: 1) fewer states are competitive; 2) there’s less and less ticket-splitting, so races for Congress are more predictable based on presidential voting and 3) “candidate effects,” including incumbency, are weaker, so there’s less opportunity for a candidate with strong personal qualities to overcome the partisan tide.