Smith worked as a farmer before entering Dáil Éireann at the 1969 general election as a Fianna Fáil TD for the Tipperary North constituency.

His stay in cabinet was brief; following the 1989 general election he was demoted to Minister of State at the Department of Industry and Commerce.

After the 1997 election, Fianna Fáil returned to government and Smith was appointed as Minister of State at the Department of Education and Science.

[5] In October 1997, he replaced David Andrews as Minister for Defence, and held that position until he was dropped from the cabinet in a reshuffle in 2004.

[6][7] During his tenure Smith dealt with the Army deafness compensation issue that ultimately resulted in claims of €300 million against the State.