Want to follow election results like a pro? Here's what to watch in key states

As thousands of U.S. counties and towns report vote totals, it can be hard to figure out when the results reported so far will reflect the outcome. The first report election night might show a massive lead for one candidate, but that lead could dwindle in some races and grow in others. What’s the difference between a “mirage” and a real outcome? Past elections can provide a guide. They show that mail-in votes in recent elections have heavily favored Democrats — and that in some states, counties report those ballots first. That can create a so-called “blue mirage” that could result in only narrow victories for Democrats or even substantial victories for Republicans.