Lewis contested Rugby in 1945, Crosby in 1950, West Derbyshire in 1951, Northamptonshire South in 1955 and Darlington in 1959. He was Member of Parliament for Carlisle from 1964 until he retired in 1987. In 1983, Carlisle was the most marginal Labour seat in the country - with Lewis finishing just 71 votes ahead of the Conservative candidate.