Parker was one of the founders of the Albany (New York) Law School in 1851, and he was a member of the school's faculty for over twenty years. He was the unsuccessful Democratic candidate for Governor of New York twice, losing to Republicans John Alsop King in 1856 and Edwin D. Morgan in 1858. During the administrations of New York's Democratic governors, Parker declined several offers to reappoint him to the bench, and during the presidential administration of James Buchanan he declined appointment as United States Attorney for the Southern District of New York.