DUBLIN — Irish voters Saturday rejected a government plan to abolish the country’s much-criticized Senate, a surprise result that dealt a blow to Prime Minister Enda Kenny.
Kenny had personally campaigned for the proposed constitutional amendment to eliminate Ireland’s upper house of parliament, arguing that the Senate was undemocratic, politically toothless, and expensive in an era of budget cuts. All opinion polls during the monthlong campaign had pointed to easy passage.
Instead, voters rejected Friday’s referendum on abolishing the Senate with a 51.7 percent ‘‘no’’ vote. Turnout was just 39 percent, a typically weak figure for Irish referendums, when antigovernment voters often come out in droves.
Still, the rejection was widespread across Ireland’s constituencies. It suggested a nationwide failure by Kenny’s Fine Gael party to win the trust of voters, who had strongly backed his party when he rose to power in 2011 after Ireland’s international bailout.
Analysts particularly faulted him for refusing to debate the measure on national television. Instead, Fine Gael staged informal media events and plastered Ireland with posters arguing a ‘‘yes’’ vote would mean ‘‘fewer politicians’’ and annual taxpayer savings of $27 million.
Many analysts branded the figure an exaggeration and insignificant, given Ireland’s $187 billion national debt.
‘‘Sometimes in politics you get a wallop,’’ Kenny said.
Asked why he hadn’t agreed to a TV debate, Kenny said he had wanted to avoid ‘‘a shouting match with political leaders.’’
Supporters of keeping the Senate argued the government now must strengthen the institution. They called for the Senate to gain the power to block legislation, not merely debate and on rare occasions delay it. Only the powerful lower house of Parliament, the Dail, is directly elected and can reject government legislation.
‘‘The moral pressure for reform is now absolutely overwhelming,’’ said John Crown, an independent senator.
Any amendments to Ireland’s 1937 constitution require majority voter support in referendums. The Irish have demonstrated a tendency to say ‘‘yes’’ to pollsters, but then vote no in private, with antigovernment sentiment invariably higher than surveys suggest.
This time, unusually, both the conservative Fine Gael and most left-wing parties backed the idea of ending the Senate, with the nationalist Sinn Fein and hard-left socialists both decrying its air of privilege. Only the parties of the previous disgraced government, Fianna Fail and the Greens, opposed the measure.
Paul Murphy, an Irish Socialist Party member of European Parliament, said the result reflects ‘‘deep distrust of the government and shows that people have a desire to check and hold back the proausterity political establishment.’’
Kenny’s government enjoys the biggest parliamentary majority in Irish history and doesn’t face reelection until 2016. But it is divided over the scope of the next austerity budget due to be published Oct. 15.
Saturday’s election was the 33d referendum since the 1937 constitution was signed; 23 of the proposed amendments have passed, and nine have been rejected. The highest voter turnout was almost 71 percent, the lowest 28.6 percent.