Eleven candidates are in the race to fill the seat vacated by former junior minister Brian Hayes following his election to the European Parliament in May. They are:
Cait Keane (FG): Was elected to the Seanad for the first time in 2011 following Fine Gael's landslide victory in the general election. A party loyalist, she is expected to run in the upcoming general election.
John Lahart (FF): A councillor, he held one of the most senior advisory roles in the last government. Highly regarded by the party leadership, he will do well on his home turf of Knocklyon.
Pamela Kearns (Lab): Narrowly held on to her seat in May's local elections, having crossed the line on the 10th count. She is a local careworker and community activist.
Ronan McMahon (Ind): The sitting councillor was strongly criticised during May's local elections when he ran as an Independent Fine Gael candidate. He insists that he still has Fine Gael connections, despite not being selected by the party and subsequently being backed by the Reform Alliance.
Cathal King (SF): The bookies' favourite. He recorded a stunning vote in May's local elections which were dominated by Sinn Fein in the Dublin region.
Paul Murphy (AAA): Has yet to win a single election, despite being one of the best-known politicians on the far left. He was co-opted to the European Parliament in 2011 following the election of his mentor, Joe Higgins, to the Dail.
Other candidates: Nicky Coules (People Before Profit), Francis Noel Duffy (Green Party), Tony Rochford (Independent), Declan Burke (Independent), Colm O'Keeffe (Independent).
Voting takes place on Friday, with results expected early on Saturday night.