[3] His popularity as a local councillor was hoped to strengthen the party's hopes of retaining the two seats which it had won in the three-seat constituency in 2002, and O'Sullivan was seen as a strong candidate to succeed Joe Walsh, who was retiring after 30 years in Dáil Éireann.
Fianna Fáil increased its share of the vote, with O'Sullivan topping the poll, and he was the first candidate to win a seat.
However, his colleague Denis O'Donovan, who had won a seat from Fine Gael in 2002, was defeated after just one term in the Dáil.
[4] Under the Local Government Act 2001, O'Sullivan vacated his council seat when elected to the Dáil.
He was arrested on suspicion of drink driving on 2 June 2008, he has apologised after failing a breath test near Clonakilty.