It's not over until Wednesday. People relaxed during Brexit.
Brexit is the dumbest false equivalence here. The only similarity is that people are going out to vote for something.
As Obama's former political campaign manager stated sometime this year, Trump has no real conceivable route to reach 270. He needs to win a whole pile of swing states that are pretty solidly in Clinton's favors. Unlike Brexit, this isn't a dumb popularity contest. Even if Trump wins the popular vote (zero serious evidence at all for this to occur), he still won't become president if he doesn't achieve 270 EVs.
The problems for Trump are many.
Most swing states are demographically diverse and Trump has pissed off literally every minority but going full racist. Reports suggest that minority turnout in Nevada, Florida and North Carolina are extremely strong. If he loses Florida, you might as call it a night since he ain't winning without it.
Then you have Trump's terrible campaign operation where he's dependent on existing Republican resources to get people to vote. That's fine in Florida, where the state party is pretty competent, but he's toast elsewhere.
Where the Deomractic Party has an all-star list helping them, from Bernie to Jay Z to Lebron James, to increase turnout, Trump doesn't really have anyone except himself and his family. He ain't appealing to anyone but his own base.
He also hasn't really got a coherent strategy wasting time by visiting areas that either don't need his support or are already lost.
So yeah Trump can win. But early polling shows he's already toast in Nevada and likely toast in Florida. And if he loses Florida and Nevada, it's game over.
Pessimism is good though. I'd rather people be worried and get out to vote, than people being optimistic and staying home "cuz they don't need to".
That's the point of a ground game (GOTV). The Democratic Party has a very strong one. Trump barely has one and it's simply not appealing to anyone but his own base.