At 9:30 p.m. ET things looked very rosy for Donald Trump in the Presidential Election, with predications at that point calling 168 Electoral College votes for the former president, with Kamala Harris back on 62. The total required to win is 270.

However, don’t be fooled by the number of states that have been called already at this point. It’s a feature of the presidential election often called the ‘Red Mirage’ and it affects the results at both state level and the popular vote.

Why does an election mirage happen?

There are a number of reasons why the vote appears skewed at a certain point in the counting process.

One is simply that States that were always going to be Trump states have reported their results early, while States, such as California, which will vote for Harris have not yet finished polling.

Another reason is that votes are cast in different ways, for example mail-in or in-person, and these are counted at different times. Where one group of voters generally tends to use one method more than another group, that can lead to a mirage.

For example, members of the Democratic Party are more inclined to use early voting options. In many places, these take longer to be counted and announced, because the tabulation of these votes can be time-consuming, as each mail-in ballot must go through several verification steps: the envelope has to be carefully opened, the voter’s signature must be meticulously matched against official records to ensure authenticity, and finally, the votes need to be scanned into the system for counting.

What’s more, geography can play a part in creating a mirage. Small, rural counties (that generally tend to trend Republican) often report their tallies faster than large, urban centers (that skew Democrat) because it’s easier to count votes when there are fewer of them. That means early in the count the Republican tally will be higher, simply because more of those votes have been counted, once the final tally is reached the mirage disappears.