McCarthy joined the United States Air Force in March 1951, and served for twenty-one months until the end of 1952, as an enlisted man.

[1] While at the Strategic Air Command, he spent a few weeks deployed to Saudi Arabia taking part in a mission to simulate the start of World War III.

In 1958, the year that saw the Democrats capture statewide offices for the first time since World War II, McCarthy managed the successful campaign for State Senate of J. Eugene McAteer.

(Art Agnos, elected mayor of San Francisco in 1988, had his political start as McCarthy's first legislative assistant, and later as the speaker's chief of staff.)

[3] Curb was so incensed at the charges that he filed a $7-million libel and slander suit against McCarthy, who ultimately won the election.

He easily won the Democratic Party nomination but was defeated in the general election by the Republican incumbent and future Governor Pete Wilson.

Upon leaving politics, he created an investment company, The Daniel Group, named for his father and located in San Francisco.

He helped found the Leo T. McCarthy Center for Public Service and the Common Good at the University of San Francisco.