Actress and presenter Oprah Winfrey
As President Trump prepares to celebrate a year in office, attention is already turning to who could challenge him in 2020.
Oprah Winfrey has been tipped to run after her rousing speech at the Golden Globes, with the television star said to be "intrigued" by the idea.
But a host of Democrats believe they can do what Hillary Clinton failed to and beat the billionaire Republican.
Here are some of the main contenders.
Vermont Senator Bernie Sanders’ progressive views attracted millions of supporters in the 2016 race to be the Democrat presidential candidate.
Although he ultimately lost out to Hillary Clinton, he has continued to promote his political group Our Revolution and travelled around the US to discuss issues from health to education.
However, Mr Sanders will be 78 in 2020 which would make him the oldest person ever to stand for presidency, and by that time will he want to take on the top job?
Barack Obama’s former Vice President Joe Biden has said he regretted his decision not to run in 2016, following the death of his son Beau in 2015, and has been critical of Hillary Clinton’s campaign.
The popular former Senator, who ran for president in 1987 and 2007, has refused to rule out running in 2020.
However, his age – he will be 77 in 2020 – and his handling of sexual harassment allegations in the 1990s against Justice Clarence Thomas, for which he has apologised, could go against him.
Massachusetts Senator Elizabeth Warren – a longtime nemesis of Trump – is likely to be the frontrunner for the Democrats should she launch a bid to run in 2020.
And she has shown signs of seriously considering running by raising more campaign money, $12.8 million (£9.4 million), than nearly any other and has groomed political connections within the party, according to US media.
Like Sanders, Ms Warren is in the left-wing populist side of the Democrats – speaking out against Wall Street and the "one per cent" – but has forged a strong relationship with the party establishment.
New York Senator Kirsten Gillibrand, occupying Hillary Clinton’s vacated seat, has gained popularity by speaking out and taking action against sexual impropriety within the US government.
She was the first to call for the resignation of fellow Democratic senator Al Franken following sexual assault allegations and said that former President Bill Clinton should have resigned over his sexual misconduct.
Since then, she has introduced legislation to reform the Senate’s sexual harassment policies.
If she ran against Trump it would sure to be a dramatic battle after she called for his resignation over sexual assault allegations to which he responded that she "would do anything" for campaign contributions – a comment she described as a "sexist smear".
California Senator Kamala Harris, the second black woman to be elected to the body, has only served one year so far but speaks up regularly on issues from immigration to health care.
The youngest potential candidate for 2020, Ms Harris has joined other Democrats on the campaign trail which gave her the chance to raise her profile in other States.
And she is seen as a tough opponent to President Trump, saying his resignation over sexual harassment claims would be in the "best interests of the country" despite being relatively new to the Senate.
A Republican challenge?
President Trump could face competition from within his own party in 2020.
Senators Ben Sasse, Ted Cruz and Jeff Flake as well as Governor John Kasich are tipped to have left the door open to challenge Trump to become the Republican presidential candidate.