Due to gerrymandering (done by both parties, but done better by Republicans), most districts are super blue or super red even if the state is purple. So you only need a few key data points and the race can be called. Super minority packed urban districts aren't going to go red and super white rural districts aren't going to go blue.
New Hampshire seems to be fine for Dems thus far. Looks more and more likely that they'll hold the Senate seat and both Congressional districts. Frankly, other than the Florida wipeout, things aren't looking horrible for Dems (they'll lose seats but nothing catastrophic). I think Virginia will be the first big test of states that have closed. I think they're only reporting EDay right now in those districts so we have a ways to go.