This could be one of the largest Democratic presidential fields in history. There are dozens of people who have talked about getting in: from mayors, senators and governors, to business leaders, venture capitalists and even a spiritual guru.
There are nine candidates in the race so far, with nearly two dozen others still thinking about it and another already dropping out. It's a big change from 2016 when a total of five major Democratic candidates ran.
For Democrats, it's also one of the most consequential elections ever, with the opportunity to deny President Trump re-election after a term that has outraged the left. The candidates come from different parts of the country and have differing approaches on how to win in 2020 and beat Trump.
Here's a guide to who's in, who might be in, and who is taking a pass on the 2020 Democratic presidential nomination.