The below have either announced or may announce.
Cory Booker - Senator from New Jersey
Pete Buttigieg - Mayor of South Bend, Ind.
Julián Castro - Former secretary of housing and urban development
John Delaney - Former representative from Maryland's 6th District
Tulsi Gabbard - Representative from Hawaii's 2nd District
Kirsten Gillibrand - Senator from New York
Kamala Harris - Senator from California
Elizabeth Warren - Senator from Massachusetts
Joe Biden - Former vice president
Mike Bloomberg - Former mayor of New York City
Bill De Blasio - Mayor of New York City
Eric Holder - Former U.S. attorney general
Terry McAuliffe - Former governor of Virginia
Sherrod Brown - Senator from Ohio
Amy Klobuchar - Senator from Minnesota
Tim Ryan - Representative from Ohio's 13th District
Michael Bennet - Senator from Colorado
Steve Bullock - Governor of Montana
Jay Inslee - Governor of Washington
Jeff Merkley - Senator from Oregon
John Kerry - Former secretary of state and senator from Massachusetts
Bernie Sanders - Senator from Vermont
Andrew Gillum - Former mayor of Tallahassee, Fla.
Beto O'Rourke - Former representative from Texas' 16th District