2020 election updates:

Americans are voting in large numbers on Tuesday in one of the most divisive bitter presidential elections in decades in which incumbent Republican Donald Trump is challenged by Democrat Joe Biden, both confident of big victory as polling begins.

Iran PressAmerica: Amid a resurgent COVID-19 pandemic, nearly 100 million people have already cast their ballots in early voting, putting the country on course for its highest turnout in a century.

Some 239 million people are eligible to vote this year. The mail-in ballots could take days or weeks to be counted in some states – meaning a winner might not be declared in the hours after polls close on Tuesday.

Polls opened and will close across the US at different times Tuesday, anywhere after 6 am and before 9 pm local time. 

More than 100 million Americans have voted nationwide before the polls opened on Election Day, according to a survey of election officials by CNN, Edison Research, and Catalyst.   

These votes represent more than 45% of registered voters nationwide. Eighteen states and Washington, DC, have seen more than half of their registered voters cast ballots already.

Nationwide, the more than 96 million ballots already cast represents 70% of the more than 136.5 million ballots cast in the 2016 presidential election.

Biden continues to lead over Trump with the polls indicating that the margin between the two nominees. In the key battleground states, the average lead of Biden by Tuesday morning has reduced to 2.3 percent, according to Real Clear Politics which keeps track of all major opinion polls.

National polls give a firm lead to Mr. Biden, but it is a closer race in the states that could decide the outcome.

To be elected president, a candidate must win at least 270 votes in what is called the electoral college. Each US state gets a certain number of votes partly based on its population and there are a total of 538 up for grabs.

This system explains why it is possible for a candidate to win the most votes nationally - as Hillary Clinton did in 2016 - but still, lose the election.

Control of the Senate is also at stake in these elections, with the Democrats seeking to gain control of both houses of Congress and the White House for the first time since early in Barack Obama's first term.

The coronavirus pandemic has at times overshadowed the election campaign, with the pandemic in the US worsening over the final weeks of the race. The country has recorded more cases and more deaths than anywhere else in the world, and fear of infection has contributed to an unprecedented surge in early and postal voting.

It can take several days for every vote to be counted after any US presidential election, but it is usually pretty clear who the winner is by the early hours of the following morning.

In 2016, Donald Trump took to the stage in New York at about 03:00 local time (08:00 GMT) to give his victory speech in front of a crowd of jubilant supporters.

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