Analysis of information sources in references of the Wikipedia article "History and use of the single transferable vote" in English language version.
The political party who originally nominated the member who caused the vacancy nominates a new member and the council then passes a resolution to appoint the new member.
Local electoral areas and the number of members to be elected in each are specified in a statutory instrument for each local authority area. These were most recently made in 2014 for all except Cork City, which was made in 2008.
the Fine Gael loss ultimately came about because the party's two strongest candidates were on the inside panel nominated by Oireachtas members... Both Mr Twomey and Mr Slowey were ahead of Ms Ormonde on the last count but because of the special rules governing Seanad elections, under which a set number of seats are reserved for candidates of outside nominating bodies, the Fianna Fáil candidate was elected.
We will also consider: [...] Reducing the size of local electoral areas.
the Fine Gael loss ultimately came about because the party's two strongest candidates were on the inside panel nominated by Oireachtas members... Both Mr Twomey and Mr Slowey were ahead of Ms Ormonde on the last count but because of the special rules governing Seanad elections, under which a set number of seats are reserved for candidates of outside nominating bodies, the Fianna Fáil candidate was elected.