He served in the Oireachtas for 7 years as a Teachta Dála (Territorial Decoration), and then as a Senator for 8 years. Lahiffe was elected to Dáil Éireann at the 1948 general election as a Fianna Fáil Territorial Decoration for the Galway South constituency. Lahiffe held the seat at the general election in 1954, but was ousted again at the 1957 general election.
Fianna Fáil had run three candidates in three-seat constituency, and Lahiffe was beaten by his first-time running-mate Michael Carty.
He was then elected to the 9th Seanad by the Agricultural Panel, which re-elected him in 1961. However, he was defeated at the 1965 election to the 11th Seanad.