Mitchell begins his political involvement when he supports Seán MacBride, leader of the radical republican Clann na Poblachta in the 1957 general election. He joins Fine Gael in 1967, becoming that party’s unsuccessful candidate in a by-election in 1970. He seeks a party nomination to run in the 1973 Irish general election. However he agrees not to contest the seat to allow Declan Costello, a senior figure in his party and son of former Taoiseach John A. Costello, to be elected. Costello goes on to serve as Attorney General of Ireland in the 1973-1977 National Coalition of Fine Gael and the Labour Party.
Mitchell is elected to Dublin Corporation in 1974. In 1976, at the age of 29, he becomes the youngest ever Lord Mayor of Dublin. He is an unsuccessful candidate for Dáil Éireann in the 1973 general election in Dublin South-West and loses again in the 1976 by-election in the same constituency, to Labour’s Brendan Halligan.
In the 1977 general election he is elected to the 21st Dáil for the new constituency of Dublin Ballyfermot. With the party’s loss of power in 1977, the new leader, Garret FitzGerald appoints Mitchell to the Party’s Front Bench as spokesman on Labour. At the 1981 general election Mitchell is elected for the Dublin West and Fine Gael dramatically increases its number of seats, forming a coalition government with the Labour Party. On his appointment as Taoiseach, Garret FitzGerald causes some surprise by excluding some of the older conservative ex-ministers from his cabinet. Instead young liberals like Mitchell are appointed, with Mitchell receiving the high profile post of Minister for Justice, taking responsibility for policing, criminal and civil law reform, penal justice, etc. The Fine Gael-Labour government collapses in January 1982, but regains power in December of that year. Mitchell again is included in a FitzGerald cabinet, as Minister for Transport.
As Minister for Transport, Mitchell grants the aviation license to a fledgling airline called Ryanair on November 29, 1985. This is granted despite strong opposition by Ireland’s national carrier Aer Lingus. The issue of the license breaks Aer Lingus’ stranglehold on flights to London from the Republic of Ireland.
Mitchell, who is seen as being on the social liberal wing of Fine Gael, is out of favour with John Bruton when he becomes Fine Gael leader in 1990. When Bruton forms the Rainbow Coalition in December 1994, Mitchell is not appointed to any cabinet post.
Mitchell contests and wins Dáil elections in 1977, 1981, (February and November) 1982, 1987, 1989, 1992, 1997. He runs for his party as its candidate to become a member of the European Parliament in the 1994 and 1998 elections. He also is director of elections for Austin Currie, the Fine Gael candidate, in the 1990 presidential election.
In 2001, Bruton is deposed as Fine Gael leader and replaced by Michael Noonan. Mitchell serves as his deputy from 2001 to 2002. He also chairs the key Oireachtas Public Accounts Committee. The Committee’s work under his chairmanship is widely praised for its inquiry into allegations of corruption and wide-scale tax evasion in the banking sector.
Though regarded in politics as one of Fine Gael’s “survivors,” who holds onto his seat amid major boundary changes, constituency changes and by attracting working class votes in a party whose appeal is primarily middle class, Mitchell loses his Dublin Central seat in the 2002 general election. That election witnesses a large scale collapse in the Fine Gael vote, with the party dropping from 54 to 31 seats in Dáil Éireann. Although Mitchell suffers from the swing against Fine Gael in Dublin, he is not aided by the fact that Inchicore, which is considered his base in the constituency has been moved to Dublin South-Central. He chooses not to run in that constituency as his brother, Gay, is a sitting Teachta Dála (TD) running for re-election for that constituency.
Mitchell earlier has a liver transplant in an attempt to beat a rare form of cancer which had cost the lives of a number of his siblings. Though the operation is successful, the cancer returns. Although he appears to be making a recovery, Jim Mitchell ultimately dies of the disease on December 2, 2002.
His former constituency colleague and rival, Taoiseach Bertie Ahern, describes Jim Mitchell as having made an “outstanding contribution to Irish politics.”