 McCormack was a Massachusetts delegate to the 1964 Democratic national convention.McCormack was the Democratic nominee for Governor of Massachusetts in 1966, when he lost to Republican incumbent John A. Volpe, the first time that the term of that office was extended from two to four years.Although no longer in public office, he remained a political insider and worked as a development lawyer in Boston real estate while his friend, Kevin H. White was mayor of that city.