In 1990, Weld announced his candidacy for Governor of Massachusetts to replace the out-going Michael Dukakis. Although Republicans made up under 14% of the Massachusetts electorate and a Republican had not won the gubernatorial election since 1970, Weld's liberal stances on social issues made him a viable candidate for office in the heavily Democratic state. At the state Republican convention, party officials backed Steven Pierce over Weld, and initial polling had Pierce ahead by 25 percentage points. However, Weld gained enough support to force a primary, and in an upset election, he won the Republican nomination over Pierce by a 60–40 margin.