The constituency has been a marginal seat between the SNP and Labour since the 1973 by-election. Although Labour won the seat in that by-election, the SNP established itself as the clear challenger and continued to advance, winning the seat in the next general election. Labour were thought to have underperformed in not winning the seat back in the 1979 general election, and the choice of the former Communist Jimmy Reid as Labour candidate was blamed for the loss. John McAllion regained the constituency for Labour at the 1987 general election.