In addition to over the 200 current members of Congress, governors and other prominent office holders, there is a long list of groups endorsing Joe Biden for president. This list on Wikipedia is constantly being updated:
Political organizations:
American Bridge 21st Century[5]
Brady Campaign[90]
Democratic Majority for Israel[91]
EMILY's List[92]
Everytown for Gun Safety[90]
Giffords[90]
Indivisible[93]
Jewish Democratic Council of America[94]
J Street PAC[95]
League of Conservation Voters[96][97]
Moms Demand Action[98]
MoveOn[99]
NARAL Pro-Choice America[100]
National Organization for Women[101]
Natural Resources Defense Council[96]
NextGen America PAC[97]
Planned Parenthood action fund[100]
Population Connection Action Fund[102]
Priorities USA Action[103]
Sierra Club[96]
Students Demand Action[90]
Labor unions:
Actors' Equity Association, representing 51,000[105]
AFL–CIO, representing 12,500,000[106]
North Carolina State AFL–CIO representing 100,000[107]
North Shore AFL–CIO[108]
Amalgamated Transit Union, representing 200,000[109]
American Federation of Government Employees, representing 750,000[110]
American Federation of State, County and Municipal Employees, representing 1,600,000[105]
American Federation of Teachers, representing 1,700,000[105]
Communications Workers of America, representing 700,000[105]
International Alliance of Theatrical Stage Employees, representing 150,000[111]
International Association of Bridge, Structural, Ornamental and Reinforcing Iron Workers, representing 130,000[112]
International Association of Sheet Metal, Air, Rail and Transportation Workers, representing 203,000[113]
International Brotherhood of Electrical Workers, representing 775,000[114]
International Federation of Professional and Technical Engineers, representing 80,000[115]
International Union of Bricklayers and Allied Craftworkers, representing 75,000[107]
International Union of Operating Engineers, representing 400,000[105]
Laborers' International Union of North America, representing 500,000[116]
National Association of Government Employees, representing 100,000[117]
National Education Association, representing 3,000,000[118]
National Nurses United, representing 225,000[105]
Service Employees International Union, representing 2,000,000[119]
UNITE HERE, representing 300,000[107]
United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry, representing 366,000[120]