In 1980, he returned to New York City and won the Democratic primary election to represent the East Side of Manhattan in the House of Representatives; he lost the race to Republican incumbent, Bill Green (not related). In 1981, Green, with songwriter Harry Chapin, founded the New Democracy Project, a public policy institute in New York City. He ran it for a decade. During the 1984 presidential election, he served as chief speechwriter for Democratic candidate Senator Gary Hart, who ran second in the primaries.