Like fivethirtyeight.com, it has a good state-by-state breakdown of how the parties are doing. The thing to pay attention to is the light coloured states. Those are the states that the candidates will be spending most of their time. Whatever else the national polls are saying, it is the electoral college numbers that matter most.
Here’s the map from fivethirtyeight.com. The light coloured states like Nevada, Colorado, Montana, etc are important, especially the bigger states like Ohio (20 electoral college votes) and Florida (27).