 He joined the Labour Party in 1970 and became a prominent campaigner as Vice Chairman of the group Scottish Labour Against the Market during the 1975 referendum on continuing British membership of the Common Market.He was selected to oppose the sitting MP, the Shadow Secretary of State for Scotland, Teddy Taylor, at the 1979 general election in the Glasgow Cathcart constituency.The changing demographics of the area and Labour's increasing popularity in Scotland made it a winnable seat, and Maxton's victory was made more likely by the Conservative Party's strident opposition to the Scottish National Party, which drove some of its voters back to Labour.