Businessman Tom Steyer, former South Bend Mayor Pete Buttigieg and Sen. Amy Klobuchar suspended their campaigns in the days leading up to Super Tuesday
Massachusetts Senator Elizabeth Warren and former New York City Mayor Mike Bloomberg followed suit after disappointing Super Tuesday results.
Here's a list of all the candidates in the race for the Democratic nomination (in alphabetical order):
Former Vice President Joe Biden
The former vice president and senator from Delaware announced his bid April 25 in an online video.
In the video, he denounced the white supremacists who marched on Charlottesville in 2017 and Trump's response, calling it a "defining moment for this nation in the last few years."
"We are in a battle for the soul of this nation," Biden said in the video.
Biden entered the race with the kind of name recognition that made him a de facto front-runner. But he's also faced questions about accusations from women about unwanted touching, money, messaging, age, identity and ideology in a political environment vastly different from the one he began his career in decades ago.
Rep. Tulsi Gabbard, D-Hawaii
Democrat and Iraq War veteran Gabbard announced her presidential bid in January 2019 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. Bernie Sanders
After a 2016 campaign that saw him amass millions of supporters even as he finished second to Clinton, Sanders entered the 2020 race in February 2019, predicting victory and pointing to the progressive ideas he had championed as an outsider during the last cycle, like "Medicare for All" and free college tuition, that have since become increasingly mainstream.
In an email to supporters announcing the launch of his campaign, Sanders further took aim at 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," he 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."
The Associated Press and ABC News contributed to this report.