As president of the AAU, he advocated for the United States to boycott the 1936 Summer Olympics in protest of the antisemitic and racial policies of Nazi Germany.
He was the Democratic Party nominee for mayor of New York City in the 1937 election, but lost to Fiorello La Guardia.
[4] Mahoney was a high jumper, and qualified for the 1906 Summer Olympics, but did not compete as he was attending law school.
[4][6] In September 1912, William Jay Gaynor, the mayor of New York City, appointed Mahoney and Harry M. Rice as Commissioners of Accounts, succeeding Raymond B.
[10] In January 1923, Governor Alfred E. Smith appointed Mahoney to the New York Supreme Court to fill the vacancy caused by the retirement of Samuel Greenbaum.
In December 1934, Mahoney was elected president of the Amateur Athletic Union (AAU), succeeding Avery Brundage, who had not run for reelection.
[16] Mahoney led the effort to push the United States to boycott the 1936 Summer Olympics, held in Berlin, because of the discrimination of Nazi Germany against non-Aryan athletes.
Copeland also ran for the Republican Party nomination against Fiorello La Guardia, the incumbent mayor and a supporter of the New Deal, and lost.
[28] In 1945, La Guardia appointed Mahoney to a committee that was requested by Larry MacPhail and Branch Rickey to examine the status of African American baseball players.
He called for a draft movement to encourage Dwight D. Eisenhower to run as a Democrat in the 1948 United States presidential election instead.