It could be due to Trump's post-nomination bump, but these close nat. polls between him and Hillary is starting to become a trend. This should be troubling for the Democrats, who I bet thought this race would be a landslide a month ago against Trump.
Why would it be troubling? Hillary has had her worst stretch of time in a while and she still has a small but consistent edge. Her numbers will grow once Bernie is out. Not to mention, Obama and Romney were always very close in the national popular vote, but we saw what happened there: Built-in Democratic advantages took Obama over the edge. There's nothing to suggest that won't happen this time; in fact, the opposite is true, as Trump seems to have rejected data and ground-game organization outright.
If this is, on balance, what the race looks like when things are bad for Hillary, I'm more than optimistic.
