These states could decide the US presidential election

The US presidential election will be decided by about a dozen states that could swing to either President Donald Trump, a Republican, or his Democratic challenger Joe Biden.

These states will play a critical role in delivering the 270 Electoral College votes needed to win the White House. Due to a surge in mail voting amid the coronavirus pandemic - as well as the states' varying rules for when ballots can be counted - the final results for all the states are expected to take days to be revealed.

Arizona

Electoral votes: 11

Polls have closed.

Rating in presidential contest: Leaning Democratic

Other key races: Democratic challenger Mark Kelly appears to have won the US Senate seat currently held by Republican Martha McSally.

Vote counting: Arizona has no-excuse absentee voting. All ballots had to arrive by the close of polls on Election Day. Ballots could be scanned and tabulated starting 14 days before Tuesday but results not reported until after polls closed on Election Day.

Georgia

Electoral votes: 16

Polls have closed.

Rating in presidential contest: Leaning Republican

Other key races: The race for one US Senate seat will proceed to a two-way runoff between a Democrat and a Republican. The other race is considered competitive.

Vote counting: Georgia has no-excuse absentee voting. Ballots had to be received by clerks by the close of polls on Election Day. Ballots could be opened and scanned on receipt, but they could not be tallied until after the polls closed on Tuesday. Officials in Fulton County, home to Atlanta and a tenth of all Georgians, warned on Tuesday that its vote count would not be finalized until Wednesday after a burst pipe delayed absentee-by-mail ballot processing for at least two hours, according to local reports.

Pennsylvania

Electoral votes: 20

Polls have closed.

Rating in presidential contest: Leans Democratic

Other key races: Competitive US House contests in the 1st and 10th Districts

Vote counting: Pennsylvania has no-excuse absentee voting, and ballot counting could begin at 7 a.m. on Election Day. Last week, the US Supreme Court let stand a ruling by Pennsylvania's top court that officials in the state could accept mail-in ballots three days after Tuesday's election, so long as they were postmarked by Election Day. Election officials in Philadelphia, the state's largest county and a Democratic stronghold, said on Tuesday evening they expected to release more results between midnight and 1 a.m. EST (0500 and 0600 GMT) on Wednesday, with more updates later that morning.

Wisconsin

Electoral votes: 10

Polls have closed.

Rating in presidential contest: Leans Democratic

Other key races: No governor or US Senate races on the ballot

Vote counting: Wisconsin has no-excuse absentee voting. The state's election officials cannot count mail-in ballots that arrive after Election Day, the US Supreme Court ruled on October 26. Ballots could not be counted until polls opened on Tuesday. The Board of Elections director in Milwaukee County, the state's most populous, said on Tuesday evening that the county's presidential vote count would not be completed until at least 6 a.m. EST on Wednesday due to the amount of absentee ballots received.

Michigan

Electoral votes: 16

Polls have closed.

Rating in presidential contest: Leans Democratic

Other key races: Competitive US Senate contest

Vote counting: Michigan has no-excuse absentee voting. Ballots had to arrive at clerks' offices by the close of polls on Election Day. Some densely populated jurisdictions in the state, such as Detroit, began sorting absentee ballots on Monday, but the vast majority did not. Clerks could begin scanning and counting absentee ballots at 7 a.m. on Tuesday. Michigan Secretary of State Jocelyn Benson said on Tuesday evening that she expected a fuller picture of the state's results in 24 hours, ahead of early projections. She said absentee ballots could top 3.3 million, while in-person voting ends at 2 million to 2.5 million.

North Carolina

Electoral votes: 15

Polls have closed.

Rating in presidential contest: Leaning Republican

Other key races: Competitive US Senate contest has not been called. Democratic Governor Roy Cooper appears to have won re-election.

Vote counting: North Carolina has no-excuse absentee voting. Absentee ballots could be scanned weeks in advance, but results could not be tallied before Election Day. In a blow to Trump, the US Supreme Court declined last week to block the state's plan to tally ballots that are postmarked by Tuesday and arrive by Nov. 12.

Nevada

Electoral votes: 6

Polls have closed.

Rating in presidential contest: Leans Democratic

Other key races: No governor or US Senate contests on the ballot

Vote counting: Nevada has no-excuse absentee voting, and ballots can be processed upon receipt. Nevada officials could begin scanning and recording ballots 14 days before the election, but results are not released until election night. Ballots postmarked by Tuesday will be counted so long as they arrive within seven days after the election.

Texas

Electoral votes: 38

Winner: Trump

Other key races: US Senator John Cornyn, a Republican, appears to have won re-election.

Vote counting: Texas voters must qualify to vote by mail, for example by being older than 65, being ill or disabled, or not being present in their voting county during the early voting period through Election Day. All voters could vote early in person. The population of a county determined when election officials could pre-process and count mail ballots. If the county has more than 100,000 people, the ballots could be counted after polls closed on the last day of in-person early voting in the state, which was October 30. Ballots will still be counted if they were postmarked by Tuesday and are received by 5 p.m. on Wednesday. For military and overseas voters, that deadline is extended through the end of business on Nov. 9.

Iowa

Electoral votes: 6

Winner: Trump

Other key races: US Senator Joni Ernst, a Republican, appears to have won re-election.

Vote counting: Iowa has no-excuse absentee voting. The ballots had to be received by the close of polls on Election Day, or by noon the following Monday if they were postmarked by Nov. 2. Election officials were allowed to begin opening ballot envelopes on the Saturday before the election and begin scanning and tabulating them on Monday.

Florida

Electoral votes: 29

Winner: Trump

Other key races: Scott Franklin, a Republican, appears to have won the race for US Representative of the 15th District. Carlos Gimenez, a Republican, appears to have won the race for US Representative of the 26th District.

Vote counting: Florida has no-excuse absentee voting. Election officials could begin scanning ballots more than three weeks before Election Day, but results could not be generated until after polls closed. All ballots had to be received by the close of polls on Election Day to be counted. Ballots flagged for signature errors can be corrected, however, until 5 p.m. on Thursday.

Ohio

Electoral votes: 18

Winner: Trump

Other key races: US Representative Steve Chabot, a Republican, appears to have won re-election in the 1st District.

Vote counting: Ohio has no-excuse absentee voting. Ballots could be scanned, but not tallied, as early as October 6. Absentee ballots were the first to be counted on election night. Mail ballots had to be postmarked by Monday and received by 10 days after Tuesday's election to be counted.

New Hampshire

Electoral votes: 4

Winner: Biden

Other key races: Governor Chris Sununu, a Republican, appears to have won re-election.

Vote counting: New Hampshire state officials have said all voters are able to cast an absentee ballot if they have concerns about Covid-19, and the ballots had to be received by 5 pm on Election Day. Ballots could be pre-processed in some jurisdictions beginning on October 29, but not counted until the polls closed on Tuesday.

Minnesota

Electoral votes: 10

Winner: Biden

Other key races: Competitive contests for the US Senate and US House in the 1st and 7th Districts

Vote counting: Minnesota has no-excuse absentee voting, and ballots must be pre-processed within five days of receipt. Beginning on October 20, ballots could be opened and logged, but the results were only tabulated after polls closed on Election Day. A federal appeals court ruled last week that the state's plan to count absentee ballots received after Election Day was illegal.