Dan was elected to the Senate on the Labour Panel in 1989 and was Fine Gael Deputy Leader in the Senate and spokesperson on Justice and Law Reform from 1992-1997. He has been a member of the Dáil since 1997, and was Spokesperson on Children until 2000 when he became Deputy Spokesperson on Health, Children and Mental Health issues. Dan was appointed Deputy Spokesperson on Health in June 2002, October 2007 and October 2010, and was appointed to the Joint Oireachtas Committee on Health by the Dáil on the proposal of An Taoiseach Enda Kenny TD in July 2013. In May 2014, Dan was elected Chairman of the Fine Gael Party.
Dan is co-founder, president and director of the Irish Association of Suicidology, a member of the International Association of Suicide Prevention, a member of the Advisory Board of the College of Psychiatry Ireland and is a director of the Irish Palatine Association. Dan has four children. His favourite film is In the Name of the Father and his favourite restaurant is Bloomers in Rathkeale, Co. Limerick.