The Democratic Party still has a long way to go to have any chance of wrestling back power from Donald Trump in 2020.
There will be no coronation for a Democrat champion to take on Trump. Instead, the party's nomination is wide open and the field of candidates is expected to be one of the biggest ever assembled.
It ranges from septuagenarian veterans of Washington to young pretenders barely known yet on the national stage. The party will have to decide whether to go with experience, or to skip a generation and try new blood.
Here are all the Democrats who have announced they will be running.
The US Senator of Massachusetts announced on December 31 she had formed an exploratory committee for a presidential run in 2020.
The following week, Ms Warren informally kicked off the nominating fight on a visit to Iowa, condemning the corrupting influence of money on politics and lamenting lost economic opportunities for working families.
After weeks of criticism over her claims of Native American heritage, Ms Warren formally launched her 2020 presidential campaign in February, saying she is fighting for all Americans.
Warren, 69, has made workers’ rights, fair wages and access to healthcare central to her campaign.
“This is the fight of our lives. The fight to build an America where dreams are possible, an America that works for everyone,” Warren said. “And that is why I stand here today: to declare that I am a candidate for President of the United States of America.”
Her ancestry drew fresh scrutiny in early February with the discovery that she described her race as American Indian on a form to join the Texas legal bar in the 1980s.
Warren has repeatedly apologized, saying the claim was based on “family lore”, and she now understands tribal sovereignty dictates membership.
The Independent senator for Vermont, who had announced he was taking a second shot at the Democratic nomination, has formally kicked off his presidential campaign.
He forcefully made the case that he is nothing like fellow New Yorker Donald Trump, proclaiming himself the Democrat best prepared to beat the incumbent in 2020.
"My experience as a child, living in a family that struggled economically, powerfully influenced my life and my values. I know where I came from," Sanders boomed in his unmistakable Brooklyn accent. "And that is something I will never forget."
He blindsided Hillary Clinton with an insurgent campaign from the Left in 2016 which energised young voters in a surge that drew comparisons with Labour leader Jeremy Corbyn, but ultimately fell short.
Mr Sanders’s age – he would be 79 on inauguration day if he won – is a concern. But he also has a loyal and established network of activists who could be remobilised.
One key lesson Mr Sanders learned from 2016 was that not enough groundwork had been done in the southern states, where Mrs Clinton won easily. His other weakness was foreign policy and in recent months he has been speaking to experts to widen his knowledge.
He has also been assiduously visiting Iowa and New Hampshire, the first two states to vote in the 2020 primaries. Millions of viewers have been watching events about healthcare that he streams live on Facebook. There are podcasts too.
Should he win the Democratic nomination and take on Mr Trump there would undoubtedly be fireworks. As for what nickname Mr Trump would give him, we already know. The president has christened him "Crazy Bernie".
The former San Antonio mayor has been widely tipped as a rising star in the Democratic Party for years and announced his presidential campaign on January 12.
“I’m running for president because it’s time for new leadership. Because it’s time for new energy,” the 44-year-old said. “And it’s time for a new commitment to make sure that the opportunities I’ve had are available for every American.”
Mr Castro is the grandson of a Mexican immigrant and would be the first Hispanic elected president. He served as housing and urban development secretary during Barack Obama’s presidency.
Mr Castro has sought to use his family’s personal story to challenge Mr Trump’s border policies – including criticising the president by name in his launch speech.
“Yes, we must have border security, but there is a smart and humane way to do it. And there is no way in hell that caging children is keeping us safe,” Mr Castro said.
The Democrat congressman from Maryland was the first to throw his hat into the ring when he made his announcement in September, 2017.
The 55-year-old said he was not seeking a fourth term in Congress, instead devoting time and money to his White House campaign.
Mr Delaney launched a pre-emptive strike to win some name recognition.
“I think am the right person for the job, but not enough people know that,” he told the Telegraph at the time at a gathering of around 40 Democratic activists held in a suburban home in southern New Hampshire.
“So the way I solve that problem is by getting in early and spending more time.”
Mr Delaney’s pitch is unashamedly moderate. This could prove a weakness at a time when some Democrats have buyer’s remorse at having opted for Hillary Clinton rather than Bernie Sanders, whose campaign captured the public imagination.
Gabbard, an Iraq War veteran who is the first Hindu elected to Congress and the first member born in the US territory of American Samoa, said “the issue of war and peace” would be the main focus of her campaign.
The 37-year-old’s run would not be without controversy. In 2016, she alarmed fellow Democrats when she met with Donald Trump during his transition to president and later when she took a secret trip to Syria and met with President Bashar Assad, who has been accused of war crimes and genocide. She questioned whether he was responsible for a chemical attack on civilians that killed dozens and led the U.S. to attack a Syrian air base.
She said she doesn’t regret the trip and considers it important to meet with adversaries if “you are serious about pursuing peace”. She also noted that the 2003 invasion of Iraq was based on faulty intelligence and said that she wanted to understand the evidence behind the Syria attack.
Gabbard was one of the most prominent lawmakers to back Sanders over Hillary Clinton in the 2016 Democratic presidential primary. Her endorsement came in dramatic fashion, with her resigning as a vice chairwoman of the Democratic National Committee to express her support.
Democratic US Senator Kirsten Gillibrand, an outspoken Donald Trump critic and champion of women’s issues including the #MeToo movement, has announced she is running for president.
“I’m going to run for president of the United States, because as a young mom I’m going to fight for other people’s kids as hard as I would fight for my own – which is why I believe that healthcare should be a right and not a privilege,” the senator told Stephen Colbert on his CBS television late night talk show.
Her goals will include putting gender at the fore of her campaign, combating “institutional racism”, taking on special interests and entrenched systems of power in Washington, and fighting against political “corruption and greed.”
“I know that I have the compassion, the courage, and the fearless determination to get that done,” she added.
The 52-year-old from upstate New York said she was forming an exploratory committee, a crucial legal step for a candidate to run for president, just days before travelling to the early voting state of Iowa.
Kamala Harris, a first-term senator for California, chose Martin Luther King Day to launch her presidential campaign, in a nod to the historic nature of her candidacy.
Born to an Indian mother and a Jamaican father, the 54-year-old former prosecutor would break several barriers if elected president.
An aide on her campaign said the announcement was also timed to mark 47 years since Shirley Chisholm, the first black woman elected to Congress, became the first black woman to seek the Democratic nomination for president.
Announcing her bid on ABC’s Good Morning America programme, Ms Harris said: “The future of our country depends on you and millions of others lifting our voices to fight for our American values. That’s why I’m running for president of the United States.”
Her supporters believe she has a broad enough appeal to gain traction with a Democratic Party that is increasingly non-white and fuelled by women who feel alienated by President Donald Trump’s policies.
Ms Harris has also chosen to hold her first campaign event in South Carolina, a state where black voters are the dominant force in the Democratic primary, rather than the traditional first stops of Iowa and New Hampshire, the two predominantly white states that open the primary vote.
Pete Buttigieg, a little known 37-year-old mayor, has also thrown his hat into the ring saying America needs a “new generation” of leaders.
Seen as a rank outsider, he would become the country’s first openly gay president if he managed to win his party’s nomination and then defeat Donald Trump.
The two-term mayor of South Bend, a city of 100,000 people in Indiana, was named by former president Barack Obama on a list of gifted young Democrats, in an interview published in November 2016.
In a short speech and campaign advert, Mr Buttigieg framed the White House bid around his youth as he called for a clean break with the leaders of the past.
Mr Buttigieg is a Harvard University graduate, Rhodes scholar and former McKinsey consultant who has held no national political office. He turned 37 on Saturday – just two years older than the age minimum to run for president dictated by the US Constitution – and would be the youngest-ever Oval Office occupant if he got there.
Amy Klobuchar joined the 2020 White House race on February 10, adding a pragmatic voice from the heartland state of Minnesota.
The Minnesota Senator Amy Klobuchar has positioned herself as the most prominent Midwestern candidate in the field, as her party tries to win back voters in a region that helped put Donald Trump in the White House.
In a speech that was almost a point-by-point rejection of the president’s policies and the country’s toxic divides, she told supporters: “We are tired of the shutdowns and the showdowns, of the gridlock and the grandstanding.”
“Enough is enough. Our nation must be governed not from chaos but from opportunity,” she added.
Ms Klobuchar, the 58-year-old granddaughter of an iron miner, made the announcement before a heavily bundled-up crowd under gray and snowy skies in a park along the Mississippi River, as volunteers passed out handwarmers.
In a year when many Democrats say their top priority in a candidate is an ability to defeat Trump, Ms Klobuchar’s words seemed – time after time, issue by issue – to target the president.
She said that if elected she would return to the international climate treaty on “Day One”. She promised more stringent gun laws and set a target of universal health care, while calling for America to support its troops, diplomats and intelligence officers.
“They deserve better than foreign policy by tweet,” she said.
The Texan, who gained a national following with his long-shot election battle against US Senator Ted Cruz last year, is set to announce his intention to seek the 2020 Democratic presidential nomination.
Mr O'Rourke, a 46-year-old former three-term US representative from West Texas, will make his announcement via video on social media at 7:30 a.m. EDT (1130 GMT) on Thursday, a source close to the campaign told Reuters on Wednesday.
"I'm really proud of what El Paso did and what El Paso represents," Mr O'Rourke said of his hometown in a text to TV station KTSM, which first reported his entry into the race. "It's a big part of why I'm running. This city is the best example of this country at its best."
Regardless of his defeat in the Senate race against Ted Cruz in Texas, Mr O'Rourke is being widely talked up as a White House contender.
He has been a US congressman for six years, which is enough of a legislative record for him to run. In the Texas campaign the 46-year-old proved an ability to raise prodigious amounts of money across America.
Matt Angle, a Democrat strategist, said: "Talent and charisma translate and the notion of waiting in line is going away. There is a vacuum at the top for somebody to really step into a leadership role."
Barack Obama’s vice president continues to top polls when voters are asked who they want as the Democrat 2020 candidate – though that does not mean too much at this early stage.
Mr Biden is actively considering a bid and explained in his autobiography last year that he would have probably challenged Hillary Clinton in 2016 but for the death of his son Beau.
Strengths would include Mr Biden’s potential for winning back Trump voters and his track record at the top of government. Weaknesses? He is 75 – older than the president – and could be framed as too establishment.
The junior US senator from New Jersey has styled himself a "street fighter" and there is little doubt he would love to take on Mr Trump.
Mr Booker, a 6ft 4in former star college athlete, is clearly a major contender. He said recently: "I am so determined to fight and stop Donald Trump."
Mr Booker is 48, teetotal, vegan and engages in intermittent fasting, a fad diet. He is one of only three black US senators. Underlying all his convictions is an unshakable Baptist faith.
His academic CV is impeccable - political science at Stanford, a Rhodes scholarship to Oxford, going on to study law at Yale.
Barack Obama's attorney general for six years has not been shy about suggesting he could run.
There have been a flurry of public speeches and media appearances already, and he is an ideal candidate to take up the Obama mantle.
Mr Holder, 67, stirred up controversy recently when he said of Republicans: "When they go low, we kick them."
As attorney general he led a legal defence of drone strikes, and moved terrorist prosecutions to civilian courts. He has also been a high profile advocate for voting rights.
The California lawyer has been propelled to prominence by representing Stormy Daniels, the porn star who claims she had an affair with Donald Trump over a decade ago.
Mr Avenatti's indication that he could run for the Democratic nomination was initially treated with scepticism, but he is clearly serious.
He has a long background in politics, working on campaigns and conducting opposition research, and has been making exploratory trips to the early voting states of Iowa and New Hampshire.
Mr Avenatti, 47, is a consummate TV performer and has argued that the Democrats need someone like him who can "fight fire with fire".
Out of the running
Just as he had done several times before, the 76-year-old billionaire flirted with a White House run for 2020.
But early in March, the former New York city mayor announced he would not stand.
Mr Bloomberg said that while he thought he could beat Donald Trump he was not sure he would win the Democratic nomination given the competitive field.
Instead Mr Bloomberg pledged to spend his next two years pushing for the policy changes, such as tighter gun controls and tackling climate change, in which he believes.