McDowell was a junior counsel on the legal team that defended the murderer Malcolm MacArthur in the notorious GUBU case.

[4] When Desmond O'Malley was expelled from Fianna Fáil in 1985, McDowell immediately wrote to him in support, becoming a founding member of the Progressive Democrats (the PDs).

At various times, he served as a member of the Progressive Democrats front bench in roles as spokesman for foreign affairs, Northern Ireland and finance.

In July 1999, while the PDs were in a coalition government with Fianna Fáil, McDowell was appointed Attorney General of Ireland, a position he held until 2002.

He was a strong opponent of the policies of Sinn Féin and the Provisional Irish Republican Army, and often took a harder line than his coalition partners, Fianna Fáil.

[15] McDowell launched far-reaching reforms of the Garda Síochána and introduced severe penalties (up to five years in jail) for Gardaí who leaked information under the Garda Síochána Act 2005,[16] after the force was extensively criticised by the Morris and Barr Tribunals and he was embarrassed by high-profile leaks of his plans for the force to newspapers from high-level Gardaí.

[20] Related to the defamation reforms, McDowell also proposed a new privacy law which was heavily criticised by the newspaper industry.

[21][22] In 2006, he established the Balance in Criminal Law Review Group, and in 2007 oversaw the enactment of their recommendation to roll back the right to silence.

[44] On 7 September 2006, Mary Harney unexpectedly resigned as party leader and McDowell became the favourite to succeed her in the consequent leadership election.

During the 2007 general election campaign, the Progressive Democrats erected posters bearing the slogan, "Left wing government?

While McDowell was unveiling the poster during a press briefing in Ranelagh which was the site of his telegraph pole climb in the 2002 election; constituency opponent John Gormley of the Green party turned up to confront McDowell on the issue of an accompanying pamphlet which made misleading claims about the Green party.

[47] During the 2007 RTÉ Television election debate, McDowell remarked on the state of the opposition parties: "I'm surrounded by the left, the hard-left and the left-overs.

He was the first sitting Tánaiste to lose his seat, and his subsequent departure from politics makes him the "shortest-serving political-party leader in the history of the State".

The reaction of the press was divided: That McDowell's career in government as Tánaiste is over is partly of his own making as he courted controversy to such a fevered extent that he became the most unpopular political leader in the country.

[51] McDowell's reforms of the prison service, the Gardaí and immigration policy are a monument to his five years as Minister for Justice.

[52]The then Minister for Enterprise, Trade and Employment Micheál Martin, said he was sad to learn of his cabinet colleague's decision to resign.

McDowell opposed two proposed amendments to the Constitution of Ireland, the Thirty-ninth Amendment on the Family, which proposed to expand the constitutional definition of family to include durable relationships outside marriage, and the Fortieth Amendment on Care, which proposed to replace references to women's "life within the home" and the constitutional obligation to "endeavour to ensure that mothers shall not be obliged by economic necessity to engage in labour to the neglect of their duties in the home” with a new article on supporting care within the family.