Italian Prime Minister Matteo Renzi is set to resign on Monday after suffering a crushing defeat on Sunday in a referendum on constitutional reform, tipping the euro zone's third-largest economy into political turmoil. His decision to quit after just two and a half years in office deals a blow to the European Union, already reeling from multiple crises and struggling to overcome anti-establishment forces that have battered the Western world this year. Renzi's resignation could open the door to early elections next year and to the possibility of an anti-euro party, the opposition 5-Star Movement, gaining power in the heart of the single currency. 5-Star campaigned hard for a ‘No' vote. "I take full responsibility for the defeat," Renzi said in a televised address to the nation, adding that he would hand in his formal resignation to President Sergio Mattarella on Monday. "I will greet my successor with a smile and a hug, whoever it might be," he said, struggling to contain his emotions when he thanked his wife and children for their support. "We are not robots," he said at one point. "No" won an overwhelming 59.1 percent of the vote, according to the final count. About 33 million Italians, or more than two-thirds of eligible voters, cast ballots following months of bitter campaigning that pitted Renzi against all major opposition parties, including the anti-establishment 5-Star. Mattarella will consult with party leaders before naming a new prime minister — the fourth successive head of government to be appointed without an electoral mandate, a fact that underscores the fragility of Italy's political system. The vote ended months of campaigning for a reform that Renzi had said would bring political stability to Italy — but that opponents said jeopardized democratic checks and balances. The new prime minister, who will need the backing of Renzi's Democratic Party (PD) to take office, will have to draw up a new electoral law, with 5-Star urging a swift deal to open the way for elections in early 2017, a year ahead of schedule. "From tomorrow, we will start work on putting together 5-Star's future program and the team of people that will make up a future government," said Luigi Di Maio, tipped to be the group's prime ministerial candidate. Opinion polls put 5-Star, which wants to hold a referendum on membership of the euro, neck-and-neck with the PD. Renzi, 41, took office in 2014 promising to shake up hidebound Italy and presenting himself as an anti-establishment "demolition man" determined to crash through a smothering bureaucracy and reshape creaking institutions. Sunday's referendum, designed to speed up the legislative process by reducing the powers of the upper house Senate and regional authorities, was to have been his crowning achievement. However, his reforms so far have made little impact, and the 5-Star Movement has claimed the anti-establishment banner, tapping into a populist mood that has seen Britons vote to leave the European Union and Americans elect Donald Trump president. — Reuters