Assuming the presidential race goes the right way the next battle will be for the Senate seat in Virginia that Tim Kaine left to be the next VP.
So it really makes a difference whether the Senate is split 50-50 or we can get to 51+ tomorrow. Odds are very good we can come out of tomorrow at least 50-50, but that advantage (with Kaine as the tie breaking vote) could be short lived if the GOP gets Kaine’s seat back. That seat will be a nationalized race, like Scott Brown’s was in MA in 2010 with resources pouring in from around the country on both sides.
Whoever Gov. McAuliffe appoints would have the incumbent advantage, and Virginia is becoming more blue than purple, but if you want to worry about things that you have no control over way, way prematurely, then start worrying about whether that race is to keep the Senate in Dem hands or not.
So hitting (at least) 51 on Tuesday would be good.