Voting is underway for the 2020 US Election - but what are the battleground states that could determine the result?

If you want to know who's headed for victory, these are the 12 states to watch, based on polls, ad spending and candidate visits. Ten of them went for Trump four years ago while the other two opted for Hillary Clinton.

Trump's standing across all states surged on a booming economy a year ago but it has gone down as the coronavirus pandemic continues to ravage the U.S, especially in the swing states that will decide the presidency. And already, more than 93 million Americans have cast early ballots, smashing all previous voting pre-Election Day.

Former Vice President Joe Biden and President Donald Trump are on opposite sides of the vote-by-mail issue.  

Here's how those state shape up for Election Day:

  • Toss-ups (Arizona, North Carolina, Pennsylvania)

Bill Clinton in 1996 is the only Democrat who has won Arizona (11 electoral votes) since 1952, but most political analysts say Biden has better than a decent shot in a state Trump won by 3.5 percentage points four years ago. The average of state polls has Biden up by 1 percentage point.

The former vice president's chances have been boosted by Trump's anti-immigration policies and rhetoric that have galvanized the state's large Latino electorate and the endorsement of key GOP moderates in the state, including former Sen. Jeff Flake and Cindy McCain, the widow of revered Sen. John McCain.

Another important factor helping the former vice president is the Senate race where Democrat Mark Kelly is leading over GOP incumbent Martha McSally.

Obama's 2008 win in North Carolina (15 electoral votes) in 2008 has been the only time a Democrat won the state since Jimmy Carter won in 1976. Trump won the state by 3.6% in 2016 but the average of state polls show the president ahead by less than one point.

Why does the electoral vote matter more than the popular vote?

President Trump and President George W. Bush won the electoral vote during the election, but not the popular vote. How does the electoral college work?

The growing diversity and suburbanization of the state and a strong showing by Democrat Cal Cunningham in the Senate race are expected to help the former vice president in his race against Trump. A recent New York Times/Siena College poll found Biden rising among women, voters under 45 and African-Americans.

Trump is pinning his hopes on Pennsylvania (20 electoral votes), judging by the numerous rallies he's held in the final weeks of the campaign. Most analysts say the presidency could well be decided by the Keystone State which Biden now leads by 4.3 points based on the average of state polls.

  • Biden leaners (Michigan, Nevada, Wisconsin)

Along with Pennsylvania, Michigan and Wisconsin were reliably blue states in the Upper Midwest that pivoted to Trump in 2016.

Trump won Michigan (16 electoral votes) in 2016 with fewer than 11,000 votes (out of more than 4.8 million cast). The average of state polls show Biden on top with 5.1 points.

A recent poll done by the EPIC-MRA for the Detroit Free Press indicates that Trump is not doing as well among a core constituency that catapulted him to victory in the Wolverine State.

Four years ago, white voters without college degrees backed the president 62%-31%, according to exit polls in 2016, but the latest survey finds Trump up among those blue-collar workers by a smaller margin: 54%-39%.

The growth of the Latino population has started to make Nevada (six electoral votes) a reliably blue state, but it remains within striking distance for Trump, whose background as a casino owner gives him a natural connection to the Silver State. The average of state polls shows Biden leading by 3.6 points.

Clinton during the 2016 campaign never visited Wisconsin (10 electoral votes) and lost by fewer than 23,000 votes (out of nearly 3 million votes cast). Biden's decision to make the Badger State a priority appears to be paying off as the average of state polls has the former vice president up by 6.6 points, a margin that Trump supporters point out is not far from where it was four years ago.

Though Trump has visited the state more frequently than Biden, the Democratic challenger is winning among those casting ballots before Election Day. As of late last week, 41% of respondents to the Marquette University Law School Poll say they had already voted. Of those, 64% say they voted for Biden, 25% for Trump.

A scenario from Hawkfish says that if only 15% of mail-in votes are counted on Election Day, President Donald Trump would be ahead in all … Show more  

  • Trump leaners (Florida, Georgia, Iowa, Ohio)

Political analysts are closely watching Florida (29 electoral votes), and predicting that Trump's chances of reelection rest squarely on capturing the Sunshine State as he narrowly did in 2016. Consider that no Republican presidential candidate since Calvin Coolidge in 1924 has won the White House without Florida. The average of state polls has Biden up by one point.

Democrats built an early lead among those who had come out early to vote, but a Republican surge has helped eat away at that advantage in a state known for its razor-thin margins (Bush-Gore in 2000 anyone?) .

It's likely going to come down to the state's Latino vote. Recent polling suggests Biden is underperforming with Cuban Americans in Miami-Dade, the largest county in the state, as well as with Latino voters across Florida, which has backed the national winner in every election except one since 1964.

Georgia (16 electoral votes) has not gone blue since Bill Clinton won the Peach State in 1992. Trump won the state by 5.1 points. The average of state polls show both candidates neck-and-neck with the president pulling narrowly ahead of Biden in recent polls.

A Monmouth University poll conducted last week found that more than half (58%) of registered voters in the state said they have already cast their ballots. Biden leads among this group by 55%-43%, but the president has an advantage (48%-44%) among those who have yet to vote.

Trump won Iowa (six electoral votes) in 2016 by a comfortable margin: nearly 10 points. But the president is winning only by a little more than 1 point, according to the average of state polls.

Biden's chances may hinge on how much farmers in the Hawkeye State blame Trump's trade tariffs for their economic woes.

Ohio (18 electoral votes) is another must-win for Trump, who won the state by more than eight points in 2016 but now finds the Buckeye State a dogfight this year. Averages of state polls find Trump rising in recent polls and now holding a 1.2 point edge after the former vice president was leading for weeks.

Trump has made a personal pitch to the state, stressing his support for manufacturing jobs and trade deals he believes will benefit a state that has picked every winner since Lyndon Johnson in 1964.

  • The longshots (New Hampshire, Texas)

Two states to watch that will signal a blowout: If Trump wins Nevada or Biden wins Texas.

The state that had the closest vote margin in 2016 was not Michigan but New Hampshire (four electoral votes) where Hillary Clinton's margin was a mere 2,736 (out of more than 744,296 cast), or .3%.

So it might seem odd to call the Granite State a long-shot for Trump but each of the six state polls conducted in October has Biden up by at least eight points.

Analysts believe Biden has a better shot at winning Texas (29 electoral votes) than Trump does of capturing New Hampshire given that the polling average in the Lone Star State has the president ahead only by 1.2 points.

He won the state by nine points four years ago and no Democrat has won since Carter in 1976.

  • The original version of this article was published on our sister site, USA Today.