President Joe Biden and former President Donald Trump will face each other in the US presidential election on 5 November in what looks set to be a divisive and closely fought contest.
Several third-party hopefuls are also running.
Here is a list of the candidates:
Donald Trump
Trump, in office from 2017-2021, won almost all the party's nominating contests to be the Republican candidate, setting up the first presidential rematch in nearly 70 years. He has leveraged his unprecedented legal challenges, which include 91 indictments in four criminal cases, to boost his popularity among his base and raise money.
Trump, 77, has said without evidence that the criminal charges he faces are a Democratic conspiracy designed to keep him from winning, a claim the US Justice Department has denied. Some of his legal challenges have reached the Supreme Court, which ruled that he remains eligible for the ballot following the 6 January, 2021, attack on the US Capitol and agreed to weigh his claim of presidential immunity in coming weeks.
If elected to another four-year term, Trump has vowed revenge on his political enemies, said he would not be a dictator except "on day one" and pledged to pardon those imprisoned over the 6 January attack. He also wants the power to replace some federal civil service workers with loyalists.
He sparked criticism from Western leaders after saying the US would not defend NATO members that failed to spend enough on defense and would encourage Russia to attack them. He also pressed congressional Republicans to stall a military aid package for Ukraine. Trump has made immigration his top domestic campaign issue, declaring he would carry out mass deportations, create holding camps and utilise the National Guard.
He would also end birthright citizenship and expand a travel ban on people from certain countries. However, his opposition to a bipartisan deal in the Senate that would tighten immigration enforcement has stalled, if not killed, the bill.
He has repeated calls to impose the death penalty on drug dealers, said other alleged criminals could be shot dead, and suggested he would unilaterally send federal troops into Democratic-run localities.
On abortion, Trump has taken credit for the US Supreme Court ruling overturning Roe v. Wade, but he has criticised some Republican-led states' six-week abortion bans. He said he supported in vitro fertilisation (IVF) treatment access after an Alabama court ruling curtailed access in the state and raised questions about reproductive rights.
He has promised other sweeping changes, including eliminating Obamacare health insurance and undoing much of the Biden administration's work to fight climate change. Trump has yet to announce a vice presidential running mate.
Democractic Party - Joe Biden
Biden launched his 2020 candidacy as an urgent bid to defend American liberties and protect democracy and has cast his reelection bid in the same light, saying Trump threatens the future of American democracy.
Biden faced no serious challenger for the party's nomination, which he clinched in March. November's election will be much tougher, with the most recent Reuters/Ipsos poll putting Biden on 39 percent, one percentage point ahead of Trump on 38 percent.
Biden, the oldest US president ever at 81, must convince voters he has the stamina for another four years in office and is more fit for office than Trump, who is just four years younger, while also combatting low approval ratings.
The economy will also factor in his reelection campaign. While the US escaped an anticipated recession and is growing faster than economists expected, inflation hit 40-year highs in 2022 and the cost of essentials is weighing on voters. Earlier in his term, Biden pushed through massive economic stimulus and infrastructure spending packages to boost US industrial output, but he has received little recognition from voters so far.
Biden's handling of immigration policy has also been criticised by Republicans and Democrats as migrant crossings at the US-Mexico border hit record highs during his administration.
He has led the response of Western governments to Russia's invasion of Ukraine, persuading allies to sanction Russia and support Kyiv, and he has been supportive of Israel in its conflict with Hamas in Gaza while pushing for more humanitarian aid. However, Biden has sought to respond to sharp criticism from some fellow Democrats for not backing a permanent ceasefire in the Palestinian territory and shifted to back a "ceasefire" rather than a "pause".
Vice President Kamala Harris, who is again Biden's running mate, also delivered recent blunt remarks calling on Hamas to back an immediate six-week ceasefire and pushed Israel for a "credible" humanitarian plan before conducting major military offensives.
Gaza health officials say more than 31,000 people have been killed, thousands of buildings have been damaged or destroyed, and residents have insufficient food, water and medical supplies. Biden faced a protest vote over his support for Israel's war in Gaza in some of the Democratic Party's nominating contests, including Michigan and Minnesota.
Democractic Party - Marianne Williamson
Best-selling author and self-help guru Marianne Williamson, 71, has relaunched her long-shot 2024 bid for the nomination on a platform of "justice and love" less than a month after dropping out.
In a 28 February statement, she said she had suspended her campaign because she was losing "the horse race" but was getting back in to fight Trump's "dark and authoritarian vision".
Despite Biden surpassing the number of delegates needed to win the nomination, she has yet to end her campaign.
Williamson previously ran as a Democrat in the 2020 presidential primary but dropped out of that race before any votes were cast.
Independent - Robert F. Kennedy Jr
An anti-vaccine activist, Kennedy, 70, is running as an independent after initially challenging Biden for the Democratic nomination, but he is far behind in polling.
It appeared that Kennedy could siphon similar shares of votes from Trump and Biden, according to the most recent Reuters/Ipsos poll, published on 14 March, that showed Kennedy was backed by 15 percent of registered voters.
Kennedy is the son of US Senator Robert F. Kennedy, who was assassinated in 1968 during his own presidential bid. A surprise Super Bowl ad heavily featuring his connection to his uncle, former President John F. Kennedy, angered his family members and prompted him to apologise.
He was banned from Instagram for spreading misinformation about vaccines and the Covid-19 pandemic but was later reinstated. He also lost a legal bid to force YouTube owner Google to reinstate videos of him questioning the safety of Covid vaccines.
Independent - Cornel West
The political activist, philosopher and academic said in June he would launch a third-party bid for president that is likely to appeal to progressive, Democratic-leaning voters.
West, 70, initially ran as a Green Party candidate, but in October he said people "want good policies over partisan politics" and announced his bid as an independent. He has promised to end poverty and guarantee housing.
Independent - Jill Stein
Jill Stein, a physician, re-upped her 2016 Green Party bid on 9 November, accusing Democrats of betraying their promises "for working people, youth and the climate again and again - while Republicans don't even make such promises in the first place".
Stein, 73, raised millions of dollars for recounts after Trump's surprise 2016 victory. Her allegations yielded only one electoral review in Wisconsin, which showed Trump had won.
- This story was first published by Reuters.