Sinn Féin's Caoimhghín Ó Caoláin topped the poll in Cavan Monaghan and was declared elected after a marathon first count.
He was more than 3,000 first preferences clear of his closest competitor, outgoing Fianna Fáil minister Brendan Smith, who polled 9,702.
His performance was well down on his showing in 2007 and party sources privately admit Fianna Fáil will only return one candidate to the 31st Dáil in place of the three they sent to Leinster House last time.
Former Ceann Comhairle Dr Rory O'Hanlon is retiring and Margaret Conlon, the first female TD to be elected in the Cavan-Monaghan constituency, accepted she had lost her seat.
Support for the Fine Gael candidates was well balanced with Senator Joe O'Reilly winning 8,333 first preferences, Heather Humpreys on 8,144 and Sean Conlan on 7,864. The fourth Fine Gael candidate, Peter McVitty, was on 3,858.
Mr Ó Caoláin's running mate, 22-year-old Kathryn Reilly, polled strongly with 6,539 first preferences but party sources thought this might fall just short of the total needed to secure the final seat. The Labour vote increased five-fold with Carlow-born Liam Hogan winning 4,011 first preferences.
Independent Joseph Duffy and Darcy Lonergan of the Green Party were eliminated after the first count.