The Senate is a problem.
Nate Silver (@NateSilver538) Tweeted:
Certainly not impossible. But you could easily have, say, the D presidential candidate win by 7 points in 2020, Dems add another 10-12 House seats… but they win “only” 3 Senate seats so the Senate is R 51-D 49 for President Beto/Harris despite two wave elections in a row. https://twitter.com/NateSilver538/status/1073775725293973504?s=17