Most of the 50 United States are expected to stay firmly Republican red or Democratic blue after Tuesday's vote, with no change from the last election.

The candidates are campaigning heavily in these so-called swing states, but their strategies aren't made any simpler by how the president is actually elected.

The popular vote in each state determines the make-up of the Electoral College, which in turn votes for the president. To win, a candidate needs the votes of at least 270 of the 538 electors.

The coronavirus pandemic has made things more complicated still, with many more people this year voting by post, which could delay the vote counts in key swing states.
In at least three states — Pennsylvania, Wisconsin and Michigan, which account for 46 electors — officials have said the final tally could take until Friday.

Here’s the current situation in 12 swing states:
Arizona: This South-western state historically has gone red, and Trump got the votes of Arizona’s 11 electors in 2016. But pollsters show a slight lead for Biden this year. Postal ballots can be counted before Election Day here. Polling stations are open from 6 am to 7 pm (1300 GMT Tuesday to 0200 GMT Wednesday).

Florida: With its 29 electors, Florida is one of the most important battlegrounds. Trump won by a thin margin in 2016, but most pollsters currently report that Biden has a small advantage. Officials can start counting mailed-in votes before voting day, so observers expect a prompt result from the Sunshine State. Voting locations in Florida are open from 7 am to 7 pm (1200 GMT Tuesday to 0000 GMT Wednesday).

Georgia: Trump won this Southern state’s 16 electors with a clear margin. Surveys currently show a tight race between Biden and Trump. Mailed-in ballots are counted on Election Day. Polling stations are open on Tuesday from 7 am to 7 pm (1200 GMT Tuesday to 0000 GMT Wednesday).

Iowa: Trump handily took this Midwestern state’s six electors in 2016, but polls show that Trump and Biden are neck-and-neck here in 2020. Mailed-in ballots are counted on Election Day. Voting locations are open from 7 am to 9 pm (1300 GMT Tuesday to 0300 GMT Wednesday GMT).

Michigan: This Rust Belt state’s 16 electors went to Trump by a razor-thin margin in 2016, but polls show Biden has a clear lead this year. Counting the ballots starts only on Election Day. Polling stations are open from 7 am to 8 pm (1200 GMT Tuesday to 0100 GMT Wednesday).

Minnesota: Democrat Hillary Clinton won this Northern state’s 10 electors by a thin margin in 2016. Polls this year show Biden has a distinct advantage. Counting mailed-in ballots starts on Election Day. Voting locations are open from 7 am to 8 pm (1300 GMT Tuesday to 0200 GMT Wednesday).

Nevada: Clinton won this Western state’s six electors by a 2-point margin in 2016. Surveys are currently showing a slight advantage for Biden. Mailed-in ballots started being counted 15 days before November 3. Polling stations are open from 7 am to 7 pm (1500 GMT Tuesday to 0300 GMT Wednesday).

North Carolina: Trump took this South-eastern state’s 15 electors by a solid 3-point margin in 2016. Surveys show a very tight race with a slight advantage for Biden. Postal votes can be counted before election day. Polling stations are open from 6:30 am to 7:30 pm (1130 GMT Tuesday to 0030 GMT Wednesday).

Ohio: Trump and Biden are head-to-head in the Buckeye State, with Trump showing a slight lead for the state's 18 electors. Trump had a definitive victory in Ohio in 2016. Mailed-in votes can be counted before Election Day. Polling stations are open from 6:30 am to 7:30 pm (1130 GMT Tuesday to 0030 GMT Wednesday).

Pennsylvania: Trump took the Keystone state by a very thin margin in 2016, but current polls show that Biden is favoured to take Pennsylvania’s 20 electors. Mailed-in votes are only able to be counted on the day of the election, and so a final tally is likely to be delayed until at least Friday. The polls are open from 7 am to 8 pm (1200 GMT Tuesday to 0100 GMT Wednesday).

Texas: This Republican stronghold with 38 electors isn’t normally considered a swing state — Trump defeated Clinton by 9 percentage points in 2016. But current surveys show just a small advantage for Trump this year. Mailed-in votes can be counted up to 12 days before Election Day in highly populated counties. Polling stations are open from 7 am to 7 pm (1300 GMT Tuesday to 0100 GMT Wednesday).

Wisconsin: This Midwestern state has 10 electors, which Trump won by a thin margin in 2016, but Biden is expected to come out ahead this year. Mailed-in votes can only be counted on Election Day, so observers expect a delay in the final tally. Voting locations are open from 7 am to 8 pm (1300 GMT Tuesday to 0200 GMT Wednesday).