Voters will cast ballots in the 2020 presidential race in the fall, but primary elections across the US to select the Democratic nominee, along with a host of local elections, have been postponed or moved or held under potentially dangerous conditions as the coronavirus pandemic has altered the course of candidates' campaigns.

Following those contests and nomination convention, the Democratic nominee will participate in presidential debates against Donald Trump this fall.

Republican parties in several states have cancelled their party primaries, presuming the incumbent will be on the ballot.

Here's an amended schedule of key election events — and a recap of what has happened so far — in the 2020 race.

14 January

Five candidates qualified for the seventh Democratic debate, which will be hosted by CNN and The Des Moines Register at Drake University in Des Moines, Iowa. On the stage will be Joe Biden, Pete Buttigieg, Amy Klobuchar, Bernie Sanders and Elizabeth Warren.

3 February

Bernie Sanders won the largest share of votes but was narrowly defeated by Pete Buttigieg for state delegate equivalents in the Iowa caucus, which captured the first votes cast in the Democratic primary race. After a chaotic release of the vote totals that ultimately led to the resignation of the state's Democratic party chair, there was heavy scrutiny over the results of the primary season's opening contest, leading to speculation for the candidates' futures as larger state primaries followed, and as the campaigns — and donors — strategised ahead of the election's crucial next few months.

7 February

ABC, WMUR and Apple News at St. Anselm College in Manchester, New Hampshire hosted the eighth Democratic primary debate.

11 February

After winning the state in a landslide in 2016, Senator Sanders won the popular vote in the New Hampshire primary, followed by a second-place finish from Pete Buttigieg and a surprise third from Amy Klobuchar. Andrew Yang, Michael Bennett and Deval Patrick later dropped out.

19 February

NBC News, MSNBC and The Nevada Independent hosted the ninth Democratic primary debate in Las Vegas, Nevada.

22 February

Senator Sanders won the Nevada Democratic caucus, which offered a glimpse of candidates' success outside the East Coast in a key state with a large Latino voting population. The senator received 24 delegates to the former vice president's nine. No other candidate passed the threshold for delegate consideration.

25 February

CBS News, Twitter and the Congressional Black Caucus Institute at The Gaillard Center hosted the 10th Democratic debate in Charleston, South Carolina.

29 February

Joe Biden won nearly 49 per cent of the popular vote in South Carolina, the first southern state to enter the primary contest, serving as a test of the strength of African-American support among the Democratic candidates. The former vice president captured 39 delegates to Senator Sanders 15. Following the primary, Tom Steyer — who came in third place — dropped out of the race. Republicans cancelled their party's primary in the state, with the incumbent president as the presumed nominee.

3 March

Fifteen states across the US held primary contests on Super Tuesday, including California, which has the largest delegate count in the US, with 415 delegates pledged to the Democratic nominee, and Texas, the second-largest delegate trove, with 228 delegates pledged to the Democratic nominee. After Pete Buttigieg and Amy Klobuchar withdrew from the race and endorsed Joe Biden, his resurgent campaign won nine states, including Texas, while Bernie Sanders won California and three other states. After disappointing finishes throughout the primary, including no victories on Super Tuesday, Elizabeth Warren ended her campaign two days later. Billionaire Michael Bloomberg also dropped out and endorsed Biden.

3-10 March

US citizens living abroad cast their votes in the Democrats Abroad primary. Bernie Sanders received nearly 60 per cent of the vote, securing nine delegates. Joe Biden received 22 per cent of the vote and four delegates.

10 March

As the coronavirus pandemic gripped the US, campaign events and rallies were cancelled, though voting was still on in in Idaho, Mississippi, Missouri, North Dakota, Washington and Michigan, a crucial battleground state for the two-man race. While Bernie Sanders won North Dakota, Joe Biden won the remaining states, with a narrow victory in Washington state.

15 March

The public health crisis framed the election's unprecedented 11th debate, hosted by CNN and Univision and giving Joe Biden and Bernie Sanders and audience-free platform from Phoenix.

17 March

Ohio postponed its primary to 2 June as Arizona, Florida and Illinois held their elections as states across the US began ordering residents to stay at home and public health warnings urged people to avoid crowds, beginning a series of controversial election events in the thick of the crisis.

Joe Biden ultimately won 296 delegates by sweeping the three states. Tulsi Gabbard ended her campaign two days later.

7 April

Wisconsin held its Democratic party despite calls from voters and the state's governor to postpone. Republican lawmakers and conservative majorities on the state and US supreme courts ultimately blocked those efforts, which also prevented absentee or mail-in ballots from being cast at a later date, forcing thousands of voters into a small number of open polling sites during the pandemic.

Joe Biden ultimately won in the state, as Bernie Sanders's supporters and other critics painted the election as illegitimate. The next day, the senator announced he was suspending his campaign.

10 April

Alaska moved its primary from 4 April with candidates competing for a share of 19 delegates. Joe Biden received 55 per cent of the vote and eight delegates, while Bernie Sanders received 45 per cent and seven delegates.

17 April

Wyoming moved its primary from 4 April with candidates competing for a share of 18 delegates. Joe Biden received more than 72 per cent of the vote and 10 delegates.

2 May

Joe Biden received more than 76 per cent of the vote in the Kansas primary, with all Democrat voters participating by mail using a ranked-choice method.

12 May

Joe Biden also received more than 76 per cent of the vote in the Nebraska primary.

19 May

Joe Biden received 67 per cent of votes in Oregon's primary, followed by Bernie Sanders, who received 20 per cent.

22-24 May

The Libertarian Party had planned to host its convention in Austin, Texas from 22-25 May as delegates selected their candidate for the ballot from among the party's declared candidates.

The convention has instead held virtually, with Jo Jorgensen emerging as the nominee – the first woman in the party's history to receive the nomination. Spike Cohen was selected as the nominee for vice president.

23 May

In Hawaii's primary, Joe Biden received 63 per cent of the vote, followed by Bernie Sanders, who received nearly 37 per cent. Biden received 16 pledged delegates. Sanders received eight.

2 June

Several primaries scheduled across the US came on the heels of growing protests against racial injustice and policy brutality as well as renewed fears of coronavirus and spikes in cases as states began to reopen.

Joe Biden won each primary in Montana, New Mexico, South Dakota and Washington DC, as well as in Indiana, Maryland, Pennsylvania and Rhode Island, which had initially postponed their elections due to the coronavirus crisis.

Controversial Republican congressman Steve King of Iowa also lost to Randy Feenstra in a primary for his House.

5 June

The former vice president clinched the Democratic Party nomination, with delayed delegate tallies pushing him past the 1,991 delegates needed to become the nominee.

6 June

Joe Biden won nominating contests in the US Virgin Islands and Guam, which participate in the primary process but not the general election.

9 June

West Virginia held its primary, originally scheduled for 12 May. Joe Biden received 65 per cent of the vote and 28 delegates.

23 June

Joe Biden received 67 per cent of the vote in New York, one of the largest delegate states behind California and Texas.

Democratic Commissioners on the state's Board of Elections initially sought to strip non-campaigning nominees from the ballots, effectively cancelling the election, but a federal judge halted the decision.

Alexandria Ocasio-Cortez of Queens and The Bronx handily defeated Democratic primary challengers in her House district and is likely to win in a re-election bid.

In Kentucky, the former vice president received 68 per cent of the vote.

30 June

Amid a wave of progressive candidates holding primary challenges against moderate Democrats, Jamaal Bowman defeated longtime New York Democrat Elliot Engel, pending absentee ballot counts.

Following mail-in ballots in Kentucky, Amy McGrath – with a slim lead over progressive challenger Charles Booker – has secured the Democratic slot to face against Republican incumbent Mitch McConnell.

7 July

Joe Biden took nearly 90 per cent of the vote from his home state of Delaware, and he received more than 86 per cent of the vote in New Jersey. Both states moved their election dates a second time from 2 June.

9-12 July

Green Party co-founder Howie Hawkins and running mate Angela Nicole Walker were selected as the third party's nominees at its convention, which was held virtually after an initial plan to hold its event in Detroit, Michigan.

11 July

Joe Biden received nearly 80 per cent of the vote in Louisiana, after election officials postponed the date a second time from April to 20 June.

12 July

Puerto Rico's primary was postponed twice over coronavirus concerns. Joe Biden collected 56 per cent of the vote.

17-20 August

Democratic delegates were scheduled to convene in Milwaukee for 2020's Democratic National Convention, where presumptive nominee Joe Biden was officially selected as the party's nominee to face Donald Trump in November. The event was originally scheduled for July but was postponed due to the coronavirus crisis. Most the event was held virtually.

11 August

Joe Biden received more than 84 per cent of the vote in Connecticut's primary, rescheduled twice following the pandemic. It was the last state to hold a presidential primary.

24-27 August

Republicans initially planned to hold the party's nominating convention in Charlotte, North Carolina, but the party moved the event to Jacksonville, Florida over social distancing disputes. As cases surged, officials in Jacksonville announced they would require attendees to wear masks indoors after the president and his campaign sought to avoid similar precautions. That prompted GOP officials and the president to announced that the Florida event will be cancelled – all convention events will remain in Charlotte, while the president and campaign used the White House as a backdrop for partisan speeches, flouting federal law.

1 September

In Massachusetts, a heavily scrutinised primary challenge to incumbent Democratic senator Ed Markey from Joseph Kennedy III ultimately failed, with an incumbent win buoyed by progressive support.

29 September

The University of Notre Dame was scheduled to host the first 2020 presidential debate, but the university withdrew from the event over health concerns. The debate is now scheduled for Case Western Reserve University in Ohio.

7 October

Republican and Democratic nominees for vice president will debate at the University of Utah, which hosts the only debate between the running mates.

15 October

The second presidential debate will take place at the Adrienne Arsht Centre for the Performing Arts in Miami.

22 October

Belmont University in Nashville, Tennessee will host the third and final presidential debate.

3 November

Election Day — voters across the US will participate in a general election to select the next president, along with other candidates that appear on local ballots.

14 December

Electoral college representatives meet in state capitols to formally cast votes.

6 January 2021

Congress enters electoral votes into the record, and the Senate president announces vote tallies.

20 January 2021