A large number of candidates have already declared that they are running and have set off on campaign trips to Iowa, New Hampshire and South Carolina, but the field continues to grow, with new campaigns launching nearly by the week.
Here's a list of the candidates who are in the race:
Sen. Cory BookerThe New Jersey senator and former mayor of Newark declared his candidacy on Feb. 1 after spending time last year campaigning for Democrats in Iowa, Nevada, South Carolina and Mississippi.
Booker has thus far campaigned on a message of unity and collective action, promising to bring Democrats and Republicans together like he has on issues such as criminal justice reform during his time in the Senate.
"I think a lot of folks are beginning to feel that the forces that are tearing us apart in this country are stronger than the forces that tie us together. I don't believe that," Booker said on "The View" the day he announced his campaign. "So, I'm running to restore our sense of common purpose, to focus on the common pain that we have all over this country."
South Bend, Indiana Mayor Pete ButtigiegButtigieg first made a national name for himself with a bid for Democratic National Committee chair in 2017 and, at 37 years old, is the youngest entrant into the 2020 race. He could also become the first gay man to be elected president.
While he trails many of his opponents in name recognition, Buttigieg argues that he could represent a generational shift in government, and speaks frequently of issues that will affect younger Americans, such as tax reform, gun control and climate change.
"I get the audacity of somebody like me talking about running for this office, but frankly it's a leap for anybody," Buttigieg said on "This Week" in February. "And yet all of the people who had that job have been mortals who just bring their experience to the table. My experience is that of guiding a city through transformation, and I think a mayor at any level has the kind of executive frontline government experience and, by the way, problem-solving experience that we need more in Washington right now."
Former Secretary of Housing and Urban Development Julian CastroCastro, who served as mayor of San Antonio, Texas before spending over two years in President Barack Obama's cabinet, announced his campaign in his hometown in January.
"I'm running for president because it's time for new leadership because it's time for new energy and it's time for a new commitment to make sure that the opportunities I've had are available for every American," he said.
In 2016, Castro was vetted by Hillary Clinton to be her running mate, but the spot ultimately went to Sen. Tim Kaine, D-Va. This year, he says he is eager to restore the style of leadership the nation had under Obama.
Former Rep. John DelaneyThe Maryland congressman was only seven months into his third term when he announced his candidacy in July 2017, becoming the first member of Congress to launch a bid in the 2020 cycle.
While Delaney, a millionaire entrepreneur and businessman before arriving in Congress, does not have the name recognition of the other likely candidates, he has already traveled to all of Iowa's 99 counties -- a right of passage for many caucus hopefuls -- and frequently discusses his pragmatic approach and desire to bridge political gaps.
"What the American people are really looking for is a leader to try to bring us together, not actually talk like half the country's entirely wrong about everything they believe," Delaney said on "This Week" in January, adding, "One of the things I've pledged is in my first hundred days, only to do bipartisan proposals. Wouldn't it be amazing if a president looked at the American people at the inauguration and said, 'I represent every one of you, whether you voted for me or not and this is how I'm going to prove it.'"
Rep. Tulsi GabbardDemocrat and Iraq War veteran Gabbard first announced her presidential bid in January in an appearance on CNN
"When we stand together, united by our love for each other and for our country, there is no challenge we cannot overcome. Will you join me?" Gabbard tweeted.
Early on in her campaign, the first American Samoan and the first Hindu member of Congress faced questions over her work in the early 2000's for an anti-gay organization run by her father, and her defense of Syrian President Bashar al-Assad, with whom she controversially met in 2017.
Sen. Kirsten GillibrandThe New York Democrat announced that she is forming a presidential exploratory committee during an appearance on CBS' "The Late Show with Stephen Colbert" in January.
"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," she said during the interview.
Gillibrand's past moderate political positions have stoked speculation that she could be a strong general election candidate, but some of her old stances, like support for gun control that once earned her an "A" rating from the NRA, could hinder her during the Democratic primaries. She has argued that her thinking on some topics has evolved since joining the Senate.
Sen. Kamala HarrisFollowing months of speculation surrounding the California junior senator, Harris officially announced her 2020 candidacy on ABC's "Good Morning America" in January.
"I love my country. I love my country," she said. "This is a moment in time that I feel a sense of responsibility to stand up and fight for the best of who we are."
If Harris were to win the 2020 presidential election, she would become the first woman and woman of color to ascend to the nation's highest office.
Former Gov. John HickenlooperHickenlooper joined the field in early March, seeking to parlay his success in growing Colorado's economy while passing environmental regulations and gun control laws into a successful presidential campaign. In a launch video, he spoke further of healing the nation's political divisions.
"I'm running for president because we need dreamers in Washington, but we also need to get things done," he says. "I've proven again and again I can bring people together to produce the progressive change Washington has failed to deliver."
Prior to his two terms as governor, Hickenlooper worked as a geologist before starting a brewery and serving as mayor of Denver, and said that the variety of experiences have one common theme.
"One thing I've shown I can do, again and again, is create teams of amazingly talented people and really address these issues that are the critical issues facing this country," he said on "Good Morning America."
Gov. Jay InsleeInslee became the first sitting governor to join the presidential field when he kicked-off his campaign in early March.
The Washington governor is currently serving his second term in Olympia after more than two decades as a member of Congress and said that while he is proud of efforts to raise the state's minimum wage and increase access to early childhood education, his presidential bid will prioritize climate change, which he labeled an "existential threat" during his launch event.
"We went to the moon, and created technologies that have changed the world," Inslee said in his announcement video. "Our country's next mission must be to rise up to the most urgent challenge of our time: defeating climate change."
Sen. Amy KlobucharKlobuchar launched her campaign on a snowy February day in Minneapolis, laying out a platform that included a constitutional amendment to overturn the Citizen's United Supreme Court decision, signing back on to the Paris climate agreement, and advocating for criminal justice reform and universal health care/
"I'm running for every parent who wants a better world for their kids," Klobuchar said at her opening rally. "I'm running for every student who wants a good education. For every senior who wants affordable prescription drugs. For every worker, farmer, dreamer, builder. For every American. I'm running for you."
The Minnesota senator is viewed favorably by some in Democratic circles for her ability to perform strongly in her home state -- part of a Midwestern region that helped President Trump to victory in 2016.
Former Rep. Beto O'RourkeO'Rourke, who rose to national prominence during his ultimately failed challenge of Texas Sen. Ted Cruz in 2018, officially announced his presidential campaign in mid-March, calling it "a defining moment of truth for this country and for every single one of us."
The former Texas congressman immediately embarked on his first ever trip to Iowa and visited Wisconsin as well during his first weekend on the trail.
Within days, O'Rourke's campaign announced it raised over $6.1 million in the first 24 hours following his announcement, topping Sen. Bernie Sanders' previous high-water mark of $5.9 million.
Sen. Bernie SandersAfter a 2016 campaign that saw him amass millions of supporters even as he finished second to Hillary Clinton, Sanders entered the 2020 race in February, predicting victory and pointing to the progressive idea he had championed as an outsider during the last cycle, like Medicare-for-all and free college tuition, that have become increasingly mainstream.
In an email to supporters announcing the launch of his campaign, Sanders further took aim at President Trump, using some of the starkest language of a Democratic candidate up to that point.
"You know as well as I do that we are living in a pivotal and dangerous moment in American history," her wrote. "We are running against a president who is a pathological liar, a fraud, a racist, a sexist, a xenophobe and someone who is undermining American democracy as he leads us in an authoritarian direction."
Sen. Elizabeth WarrenAfter establishing a presidential exploratory committee just before New Year's, Warren officially joined the race in February with an event in Massachusetts.
"This is the fight of our lives," the senator said. "The fight to build an America where dreams are possible, an America that works for everyone. I am in that fight all the way."
A prolific fundraiser whose staffers spent time in a number of early primary states assisting other Democrats, Warren admitted in September that following the midterms she would "take a hard look at running for president," becoming one of the first major names to take steps towards a run.
Marianne WilliamsonAuthor Marianne Williamson announced the launch of her campaign in Los Angeles in January after making six trips to Iowa and one to New Hampshire over the past year as she explored a bid.
Williamson is best known outside of political circles, having written a number of popular self-help books and as a "spiritual friend and counselor" to Oprah Winfrey with multiple appearances on her show and television network.
She also ran to represent California's 33rd congressional district in 2014 as an independent, finishing fourth in the open primary, after endorsements from then-Rep. Keith Ellison, former Govs. Jennifer Granholm and Jesse Ventura, and former Reps. Dennis Kucinich and Alan Grayson.
Andrew YangYang, an entrepreneur, is running a presidential campaign most commonly noted for its support of universal basic income -- a pledge to provide all Americans 18 and older with $1,000 per month.
Yang speaks frequently about both income inequality and the economic transformation that has enriched certain parts of the country while disproportionately harming regions that have failed to keep pace.
"I was stunned when I saw the disparities between Detroit and San Francisco or Cleveland and Manhattan. You feel like you're traveling across dimensions and decades and not just a couple of time zones," Yang told "Rolling Stone" in January. "None of our political leaders are willing to acknowledge the elephant in the room that is tearing our communities apart, in the form of technological change."