For the first time since 2008, the Irish government was able this autumn to bring in a largely neutral budget, without broad tax increases or spending cuts. Dublin’s streets are full of Christmas shoppers. Its property market is almost as buoyant, with rapidly rising house prices easing some of the pain of the vast mortgages inherited from the years of the Celtic Tiger bubble.

So why are the Irish, who have taken years of punishment, suddenly in such a rage? It’s not just outsiders who are asking this question.

The government fully expected to be acclaimed for having steered the country safely through a historic crisis and to be wafted all the way to re-election in 2016 on the acclamations of the citizenry. Instead, opinion polls now show that the three parties that have dominated the state throughout its history have the support of less than half of potential voters. Sinn Fein, the populist and nationalist party that has traditionally been far weaker in the Republic of Ireland than across the border in Northern Ireland, has gained significant ground, as have far-left groups.

But the most popular political option in recent polls is, essentially, “none of the above.” Almost a third of the electorate says it will vote for nonparty or micro-party candidates.

This is a rare case of change actually falling from the sky. The catalyst for this transformation is plain old water.

In a recent Irish Times poll, 33 percent of people said they would refuse to pay the charges for domestic water when they become due in the spring (and less than half of those polled said they intended to pay). This is in spite of the government’s having already made huge concessions in the face of an earlier wave of protests by reducing the average effective charge to just 160 euros (about $200) a year per household, making Irish domestic water the cheapest in Europe. Compared with many of the other tax increases endured over six years, this seems too small a measure to have such large consequences.

As, indeed, it is. The current Irish political ferment is really a case of “add water and stir vigorously” to get a whole mess of trouble. All the ingredients for mass dissatisfaction were already present — they just needed something to bring them together.