All of these Democratic contenders are vying to be the one to try and defeat President Trump and stop him from winning a second term, which is no easy task. Despite his unpopularity, Trump's approval rating has held steady, the economy is doing well, and his base is firmly behind him.
All of it points to a long, drawn-out primary followed by an intense general election.
Here are the Democrats who are running, who might be running, or taking a pass on 2020.
This story was originally published on Jan. 31, 2019.