[1][2] In 1933, Connelly began civil service with federal relief agencies based in Boston and then Washington, DC.

"[1][2][4] In 1939, he joined the staff of the House Appropriations Committee, chaired by U.S. Representative Clarence Cannon and investigated the Works Progress Administration.

[2][4] In 1940, he joined the staff of the Senate Special Committee to Investigate Campaign Expenditures, chaired by U.S. Representative Guy Gillette.

Investigators who reported to him included: Hugh Fulton, William S. Cole, Rudolph Halley, Walter Hehmeyer, Robert L. Irvin, Donald M. Lathrom, and Frank E.

In a 1967 interview with Truman Library oral historian Jerry N. Hess, Stephen J. Spingarn, Federal Trade Commission Commissioner (1950–1953), suspected that Max Lowenthal and Connelly "stuck the knife in me."

[7] Spingarn further recalled: There was an operation run, more or less, under the supervision of Max Lowenthal in the basement of the White House which was to prepare answers to the charges that McCarthy was hurling so freely during all that period and get them ready in a hurry, not wait until the lie had gone around the world before the truth has gotten its pants on.