The Electoral (Amendment) Act 2011 stipulates that a by-election in Ireland must be held within six months of a vacancy occurring.[3] The Roscommon–South Leitrim by-election was held on the same date.
Paul Murphy of the Anti-Austerity Alliance was elected on the eighth count.[4] Murphy's victory came as a surprise as Sinn Féin had performed extremely well in local elections the previous May, winning 50.3% of the first preference vote in the Tallaght South LEA and 32% in the Tallaght Central LEA,[5][6] and were widely predicted to win the seat.[7][8][9] Murphy largely campaigned on the issue of Irish Water, stating that Sinn Féin could not be trusted to oppose water charges. In the wake of a poor local election result, Labour and Fine Gael were not considered contenders for the seat while Fianna Fáil largely focused its resources on the Roscommon–South Leitrim by-election.[10]
Murphy's victory brought the issue of water charges to the forefront of political debate in the run-up to the 2016 general election, and contributed to a shift in Sinn Féin's position to one of outright opposition.[11]