Five Republican candidates are jostling to be their party's presidential nominee for the 2024 general election, while President Joe Biden is the Democratic Party's presumptive nominee, and several third-party hopefuls have joined the fray.
Here is a list of the candidates.
Donald Trump
Trump has embraced his indictments in four separate criminal cases — unprecedented for a former American president — and leveraged them to boost his popularity among Republicans and raise funds, helping to make him the Republican frontrunner with 49 per cent in the latest Reuters/Ipsos polling on his party's nomination race.
Trump, 77, has called the indictments a political witch hunt to thwart his pursuit of a second four-year term, an assertion that the Justice Department has denied. If elected again, Trump has vowed revenge against his perceived enemies and has adopted increasingly authoritarian language, including saying he would not be a dictator except "on day one".
He has promised other sweeping changes, including gutting the federal civil service to install loyalists and imposing tougher immigration policies such as mass deportations and ending birthright citizenship. He has also promised to eliminate Obamacare health insurance and impose harsher curbs on trade with China.
Nikki Haley
A former South Carolina governor and Trump's ambassador to the United Nations, Haley, 51, has emphasised her relative youth compared to Biden, 81, and Trump, as well as her background as the daughter of Indian immigrants.
Haley has gained a reputation in the Republican Party as a solid conservative who has the ability to address issues of gender and race in a more credible fashion than many of her peers. She has also pitched herself as a stalwart defender of American interests abroad, and has argued Trump's management style is too chaotic and divisive to be effective.
She earned 12 per cent support among Republicans, according to the Reuters/Ipsos survey. In state-level polls, Haley has typically led rival Ron DeSantis in South Carolina and New Hampshire, where she has secured Republican Governor Chris Sununu's endorsement.
Ron DeSantis
The Florida governor has positioned himself to the right of Trump on several key social issues such as abortion, but his campaign has struggled to gain traction and, alongside the other candidates, remains far behind the former president in the latest Reuters/Ipsos poll with 11 per cent.
DeSantis, 45, has fired staff and rebooted his campaign several times, but those steps have done little to boost his candidacy.
His campaign says it is focused on stopping Trump in Iowa, where the party will hold its first nominating contest in January. He got a lift on Nov 6 when Iowa's popular governor, Kim Reynolds, endorsed him.
Vivek Ramaswamy
A former biotechnology investor and executive, Ramaswamy, 38, started a company in 2022 to pressure firms to abandon environmental, social, and corporate governance initiatives. The political outsider has stoked grassroots chatter as a potential alternative to Trump but has failed to gain traction.
Ramaswamy is a fervent backer of the former president, and has drawn his rivals' ire for his verbal attacks at candidate debates. He has also voiced support for conspiracy theories, including suggesting that Trump supporters' Jan 6, 2021, attack on the US Capitol was an inside job, and has pledged to pardon Trump if elected.
He drew four per cent support from Republicans in the Reuters/Ipsos poll.
Asa Hutchinson
The former Arkansas governor launched his bid for the White House in April with a call for Trump to step aside to deal with the former president's first indictment. Hutchinson, 73, has touted his experience leading his deeply conservative state as proof he can deliver on policies Republican voters care about, citing tax cuts and job creation initiatives.
Hutchinson only qualified for the first Republican debate and saw zero per cent support in the latest Reuters/Ipsos poll.
Democratic Party
Joe Biden
Biden, 81, already the oldest US president ever, will have to convince voters he has the stamina for another four years in office, amid concerns about his age and poor approval ratings.
Biden allies say he believes he is the only Democratic candidate who can defeat Trump. The most recent Reuters/Ipsos poll put him at 35 per cent, the same level of support as Trump.
In announcing his candidacy, Biden declared it was his job to defend American democracy, and referred to the deadly Jan 6, 2021, attack on the US Capitol by Trump supporters. Vice President Kamala Harris is again his running mate.
The economy will 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 food and gas is weighing on voters.
Biden has led the response of Western governments to Russia's invasion of Ukraine, persuading allies to sanction Moscow and support Kyiv, and he has been supportive of Israel in its conflict with Hamas militants in Gaza.
However, he has faced sharp criticism from some within his party for failing to back calls for a ceasefire in the Palestinian territory, where Gaza health officials say more than 23,000 people have been killed, thousands of buildings have been damaged or destroyed and residents have insufficient food, water and medical supplies.
At home, he has pushed through massive economic stimulus and infrastructure spending packages to boost US industrial output, although he has received little recognition from voters for the latter.
Biden's handling of immigration policy has been criticised by Republicans and Democrats as migrant crossings at the US-Mexico border hit record highs during his administration.
Marianne Williamson
The best-selling author and self-help guru Marianne Williamson, 71, has launched her second, long-shot bid for the White House on a platform of "justice and love".
She ran as a Democrat in the 2020 presidential primary but dropped out of the race before any votes had been cast. She launched her latest campaign on March 23 and will be on the ballot in the New Hampshire primary.
Dean Phillips
Dean Phillips, a little-known US congressman from Minnesota, announced in October he would mount a long-shot challenge to Biden because he does not believe the president can win another term.
The 54-year-old millionaire businessman and gelato company co-founder announced his bid in a one-minute video posted online, saying: "We've got some challenges. ... We're going to repair this economy, and we are going to repair America."
Independents
Robert F. Kennedy Jr.
An anti-vaccine activist, Robert F. Kennedy Jr., 69, is running as an independent after initially challenging Biden for the Democratic nomination, but he is far behind in polling.
But recent Reuters/Ipsos polls show that Kennedy could harm Biden more than Trump in the presidential election, where third-party candidates have affected the outcome of US elections even without winning. He won the backing of 18 per cent of respondents when included as an option in the latest survey.
He is the son of US Senator Robert F. Kennedy, who was assassinated in 1968 during his own presidential bid. Kennedy was banned from Instagram for spreading misinformation about vaccines and the Covid-19 pandemic but was later reinstated.
He lost a legal bid to force YouTube owner Google to reinstate videos of him questioning the safety of Covid-19 vaccines.
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.
Jill Stein
Jill Stein, a physician, re-upped her 2016 Green Party bid on Nov 9, 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.
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