Leo Isacson was born in New York City on 20th April 1910. He graduated from New York University in 1931 and became a lawyer.

In 1936 the American Labor Party was formed by left-wing supporters of Franklin D. Roosevelt and the New Deal. Two years later Vito Marcantonio was elected to Congress where he represented East Harlem's 20th District. He was joined by Isacson in 1948.

In the 1948 presidential elections the American Labor Party gave its support to Henry Wallace and the Progressive Party. Isacson was defeated when attempting to be elected to the 81st Congress in 1948.

Isacson returned to work as a lawyer but later became professor of political science at Nova University. Leo Isacson died in Florida on 28th September 1996.