The surge in early voting has been largely fueled by health concerns with the US remaining in the thick of its coronavirus outbreak, and authorities warning of a dire prognosis as the number of daily cases continues to soar.
To date, nearly 100 million people have voted early either in-person at designated polling centers, or via mail, according to the US Elections Project. In some states, early turnout has already surpassed the total number of votes cast in 2016 when Democratic nominee Hillary Clinton lost to US President Donald Trump in an outcome that shocked many forecasters.
The surge in early voting has generally been comprised of Democrats who account for 45.3% of those who cast early ballots. Republicans account for just 30% of those who have voted early, perhaps owing to Trump's repeated claims that vote-by-mail is subject to fraud in 2020 race.
This year, the president is seeking a long-shot victory against former Vice President Joe Biden, with the Democratic candidate continuing to hold a comfortable lead in national polling heading into Election Day. An average of polls compiled by the Real Clear Politics website has Biden ahead by 6.7%.
But while Biden leads nationally according to most polling companies, the race is likely to come down to several key battleground states, including the races in Arizona, Florida, Michigan, North Carolina, Pennsylvania and Wisconsin, critical states Trump won in 2016. Wisconsin then went Republican for the first time since 1984, while Pennsylvania and Michigan went Republican for the first time since 1988.
Biden has the edge in all of the states except North Carolina, but his lead is far narrower in most of the states than his standing nationally.
Trump is holding North Carolina by a 0.2% margin, while Biden leads by a slim 0.9% lead in Arizona and Florida, according to Real Clear Politics.
Either candidate needs to secure 270 Electoral College votes to claim victory. Electors are allocated to states based on their population, and most states give all of their electors to whichever candidate wins the state in the general vote.
The winner-take-all model is not adopted in Nebraska and Maine, however, which instead allocate their votes proportionally based on their final outcomes.
The fact that the Electoral College ultimately decides the winner of the presidential race has led to the victor losing the popular vote twice in the past 20 years, including Trump's 2016 win when he had nearly three million fewer votes than Clinton.
With the unprecedented number of mail-in ballot cast this year many Americans may head to bed without knowing who has won the presidency.
That is, in part, due to state regulations that have delayed the processing of mail-in ballots until Election Day, such as Georgia and Michigan.
In the key state of Pennsylvania, absentee ballots will not begin to be counted until after polls close at 8 p.m. local time (0100 GMT). And at least seven Pennsylvania counties may delay counting mailed ballots until the day after the election, meaning the state's results could be delayed even further than expected.
Over 2.4 million people have voted early by mail in Pennsylvania, according to the US Elections Project.
Further down the ballot, Americans are also casting ballots on a plethora of state and local issues, as well as electing their representatives in Congress.
All 435 seats in the House of Representatives are up for grabs this year, with Democrats widely expected to maintain their considerable hold in the chamber. In the Senate, 35 of the chamber's 100 seats are being contested.
Of those, the bulk of seats at stake -- 23 -- belong to Republicans who are facing the prospect of potentially losing control of the Senate.