Vote 2020: Here's why early election results may be misleading

When the first numbers are added up on Tuesday night, they may not accurately reflect what the final vote count will be in certain key battleground states.

Of course, this is true in any election. But this year, analysts are warning to be even more wary than usual of those first results when the polls close.

That's because more voters than ever are planning to cast their votes by mail in the 2020 election. In some closely watched battleground states, like Arizona and Florida, elections officials are allowed to start counting mail-in ballots. But in other battleground states, like Wisconsin, Michigan Pennsylvania, they're not allowed to start counting mail-in ballots until Election Day.

Normally, who votes by mail and who votes in person doesn't really fall along party lines. But this year, things are different.

In Pennsylvania, for example, Democrats outnumber Republicans in early and mail-in voting by a 3 to 1 ratio. On the flip side, Republicans are expected to outnumber Democrats in day-of voting, and those are the votes that get counted first.

That's what is expected to cause a "red mirage" effect in states like Pennsylvania, at least at first.

Because in-person vote totals will be counted first in states like Pennsylvania and Wisconsin, Republican votes may be overrepresented in those early numbers and it may look like President Donald Trump has a strong lead. When mail-in votes start to get processed and counted, things are expected to balance out a bit more.

The opposite phenomenon is expected to happen in battleground states like Florida and North Carolina, where officials start counting mail-in ballots before Election Day. We may see a "blue mirage" in those states, when mail-in votes that lean heavily Democratic get reported first. That could make it look like former Vice President Joe Biden takes an early lead, but once the in-person votes start to get tallied, we'll likely see the races tighten.

While it's technically possible we know who wins the presidency on Tuesday night, it's not the most likely scenario, explains ABC News Political Director Rick Klein. He explains when he thinks we'll know who wins the election here.