The Electoral (Amendment) Act 1959 had been struck out in 1961 by the High Court as being repugnant to the Constitution of Ireland because of excessive malapportionment and never came into effect.
The Electoral (Amendment) Act 1961 relied instead on manipulating district size.
Where Fianna Fáil had less than 50% support, four-seat constituencies were used, so that Fianna Fáil would win two of four seats; where it had more than 50% support, three- or five-seat constituencies would give it two of three, or three of five.
Before signing the bill, president Éamon de Valera convened a meeting of the Council of State on 14 July to consider the legislation.
It was repealed by the Electoral (Amendment) Act 1969, which created a new schedule of constituencies first used at the 1969 general election to the 19th Dáil.