Let's remember that the US is not a democracy, it is a republic, and the President is elected by the states, not the people.
Democrats have won the popular vote in 7 out of the last 8 elections, and I would be very surprised if they didn't win the popular vote this time as well. However, the vote will come down to seven swing states where the polls are too close to call: Nevada, Arizona, Georgia, N. Carolina, Pennsylvania, Michigan and Wisconsin. Whichever candidate wins 4 or more of these states will be the next president.