PD member Cllr Brigid Teefy’s name was drawn from the bag after she and Cllr David Naughton of Fine Gael were tied on 14 votes each.
Fine Gael flew one member back from a holiday in Lanzarote for the vote after they learned that Fianna Fáil councillor Noirin Ryan was refusing to honour a party pact with the PDs.
When the vote was called she crossed the floor and voted for the Fine Gael nominee.
Cllr Deirdre Ni Chinnéide, Labour, also supported Mr Naughton.
Last Monday, Fine Gael’s Diarmuid Scully broke party ranks to win the mayoralty of Limerick with the help of Independents and Fianna Fáil. He defeated FG colleague Maria Byrne by a single vote.
Yesterday, it was the turn of Fianna Fáil to get immersed in an internal fight, with Ms Ryan ignoring pleas to toe the party line and support the PD candidate.
After she helped the Fine Gael nominee tie with Ms Teefy, County Manager Ned Gleeson picked out a slip bearing Ms Teefy’s name from the paper bag, to cheers from her supporters in the public gallery.
Ms Teefy’s PD colleague, Cllr Rose Brennan, was elected vice-cathaoirleach with the support of FF.
In this vote, Ms Ryan kept the party line and sided with the PD candidate, helping her defeat Cllr Richard Butler (FG).
Meanwhile, Mayor Scully is facing disciplinary action from Fine Gael.
It is believed his position will be discussed at a meeting of the party’s national executive. A senior source said the executive may consider expelling him.