While polls show Democrat Joe Biden holding a large lead in the national popular vote over incumbent Donald Trump, due to the nature of the Electoral College, the national vote won't decide who wins the White House. Instead, it will come to down to contests in a handful of states that have become electoral battlegrounds.

With its 20 Electoral College votes, Pennsylvania is a crucial swing state for either candidate to win if they want to become president.

Pennsylvania hasn't always been a battleground state, but the result in 2016 changed everything.

Between 1992 and 2012, the state reliably voted Democrat, but a surge in support for Donald Trump in 2016 bucked that trend, with the Republicans winning the state by 45,000 votes.

While large cities like Philadelphia and Pittsburgh voted Democrat, many rural and industrial areas in the state swung to Trump, which was a large factor in his 2016 win, along with other areas in the Rust Belt.

Both Biden and Trump have made multiple stops to Pennsylvania in recent weeks hoping to shore up support, with polls being tight.

The election website FiveThirtyEight has Biden up by five points, but the margins have mostly been around that range during this year.

However, a result may not be known on election day, with restrictions in place as to when pre-poll votes or postal votes can be counted.

While other states have already been counting their early votes well ahead of the day, Pennsylvania will begin their count when the polls open, so it might take several days for a final result to be known due to the large number of early votes.

The result may not be known on the day, but votes will begin to be counted from midday, Australian time.

Florida is the perpetual wildcard of American elections, and 2020 promises to be no different.

It was a state that Trump won narrowly in 2016 and Democrats have been hoping to win it and its 29 Electoral College votes back.

Since 1996, the candidate who won the state of Florida has won the White House and it has become a familiar stop for Biden and Trump on the campaign trail.

Polls in Florida are showing a closer race, with an average of polls showing Biden at 51 per cent compared to Trump's 48.

Unlike Pennsylvania, Florida's results are expected to be known on the day, unless it is incredibly close.

After Florida became the centre of controversy during vote counting in the 2000 election, vote counting has become faster and early votes have already been tabulated.

Among the key factors in Florida are its high proportion of Latino voters and as well as elderly voters.

Results in Florida should start to trickle through from 11am.

Michigan is one of the Rust Belt states that surprised pundits in 2016 and was taken by Trump, thanks to a wave of support from blue-collar voters. However, the win in 2016 was one of the narrowest in the campaign, with the Republicans winning by less than 12,000 votes or 0.3 per cent.

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Aside from four years ago, Michigan had been a reliable Democrat state, having been won by their candidate at each election since 1992.

Biden is ahead by six points in Michigan but some are more optimistic and have given him a 12-point lead. Expect results from the north to come through from midday.

Wisconsin is a similar scenario to its neighbour Michigan, being another surprise state Trump won last election by a narrow margin of a little more than 20,000 votes.

FiveThirtyEight currently has Biden ahead in an aggregate of polls by eight points.

While Wisconsin has an older demographic, it had voted Democrat at every election from 1988 until 2012.

Expect a slow return of votes, though, as early votes won't be counted before the day. The first results from the state will trickle through from 1pm.

Georgia is normally a Republican stronghold, but could yield some surprises on election day.

The Peach State has voted for a Republican candidate at every election since 1996, but a changing demographic in the state in recent years has led to a tightening of the electoral race between the major parties.

According to pundits, a swing to Biden in 2020 could mean it's game over for a second term for Trump, and polls have tightened.

Biden is forecast to be up by as little as one point in an aggregate of polls but some have forecast Trump being up by three points.

It may not lead to a blue wave as Democrats hope, but if it does happen, it could lead to larger swings elsewhere. Expect to see Georgia results drop from 11am.

Arizona is another state that's tipped to go back to the Republicans after Trump won it in 2016 by 3.5 points. Since 1952, it has only voted Democrat once, with the re-election of Bill Clinton in 1996.

However, Arizona could lead to an unlikely victory for Biden if the polls are to be believed, showing the Democrats up by a little more than 2 percentage points.

Results will come through from 1pm.