This list only includes endorsements by notable individuals and organizations which have been reported by reliable independent sources. Endorsement by individuals does not imply endorsement by their organization.
James Carville, political science professor, political analyst and media commentator, and head strategist of Bill Clinton's presidential campaign in 1992[12]
Selena Torres, Nevada Assemblywoman from District 3 since 2018 (co-endorsed Booker, who withdrew after Castro;[45] endorsed Joe Biden after Booker withdrew from the race)[46]
Gary Johnson, former Republican Governor of New Mexico; Libertarian nominee for president in 2012 and 2016 (co-endorsement with Bill Weld)[69] (Libertarian)
Kate Miller, former New Hampshire State Representative from Belknap's 3rd district (2008–2010)[121]
Joe Moody, Texas State Representative from District 78, House Speaker Pro Tempore[115](endorsed Julian Castro after O'Rourke withdrew from the race)[37]
José R. Rodríguez, Texas State Senate Minority Leader representing Senate District 29[115](endorsed Julian Castro after O'Rourke withdrew from the race)[37]