PHILADELPHIA -- When the first numbers are added up on Tuesday night in Pennsylvania, they may not accurately reflect what the final vote count will be.
Terry Madonna, a public affairs expert with Franklin and Marshall College, told our sister station WPVI-TV that Democrats outnumber Republicans in early and mail-in voting by a three to one ratio.
On the flip side, Republicans are expected to outnumber Democrats in day-of voting, and those are the votes that get counted first.
What is voter suppression? Tactics used against communities of color throughout history, in 2020
The early and mail-in ballots cannot be counted in Pennsylvania until Tuesday, and they must be counted by Friday.
Because of the time it takes to open and process those ballots, it is likely that Democrats will be underrepresented in the day-of count, and over-represented in the mail-in count.
Not only could Pennsylvania be undecided on Tuesday night, but it could also be an example of what some people are calling the "red mirage," an impression that Donald Trump is winning, when in fact, many Democrats haven't even had their votes counted. That edge would slowly vanish as mail-in ballots are tallied over the days that follow.
WATCH: What are my voter rights on Election Day?