Whatever the national polls may say, the basics of this election are that Democrats need to hold all the states they won in 2016, plus either a) win back Pennsylvania, Michigan, and Wisconsin, or b) win back enough of those plus enough other 2016 Trump states to get to 270 EV. Failure to achieve one of the two means Trump gets re-elected, no matter what the popular vote margin is. Now, according to 538's survey of existing polls, Michigan and Wisconsin appear to currently be firmly in the Democratic camp. Pennsylvania, unfortunately, is another matter: polls so far show it neck-and-neck. If we fail to win that one, we're going to need to pick up at least one big Republican state like Florida, or several in combination, such as North Carolina and Arizona. Now, at the moment, those states are "leaning Democratic," but it's a very slight lean. The race could go either way, depending on our efforts in those particular states. Which would suggest that, if you don't live in any of them, at least be prepared to contribute to efforts there -- and, as we get closer to November, to consider phone-banking to get out the vote in those areas.
Personally, my fear is that we could conceivably see Trump re-elected, even if he loses the popular vote in a relative landslide (by a margin of 10% or greater). 538 had previously concluded the "popular-electoral vote gap" could favor Republicans by up to 5%, but this would obviously be a lot greater. I fear this, not just because it would mean another four years of this, but because I personally can't see how another civil war could be prevented in a country where it became obvious to all that the winner by that large a margin could still be kept from office. How could anyone trust the Constitutional basis of our country again?