I'm curious how the rural areas that report early (if any) vote. I feel like if Trump has any slippage (in turnout or margin) he's toast nationally. I suspect turnout will be slightly higher in big cities and Trump is going to lose a lot of ground margin-wise in the suburbs. So I think Trump really needs to accelerate his 2016 gains in the rural areas and exurbs. Just a repeat probably won't be enough.
That's one thing I'll be looking for too early in the night. If anything, Trump needs to somehow squeeze more votes out of rural and exurban America (Pasco) than he did in 2016 because the suburbs are going to be nasty for him. Just keeping his 2016 rural and exurban margins probably isn't enough for any states to the left of Georgia.