Nate Silver : Although a House-Senate split is the most likely outcome, there's still a 35-40% chance that one party wins both chambers.

This is a unique election in which there will be big practical consequences if polls are off by even a relatively modest amount in *either* direction. Although a House-Senate split is the most likely outcome, there's still a 35-40% chance that one party wins both chambers.

— Nate Silver (@NateSilver538) October 22, 2018