Italian Prime Minister Matteo Renzi headed into a constitutional referendum this weekend insisting he could still win his fight for political survival. But in a frantic final round of campaigning, his domestic rivals vowed to knock down proposals to streamline parliament and force the centre-left leader out of office. “If Renzi wants to preserve the minimum of credibility he has left, he should not only leave the government but quit politics altogether,” former premier Silvio Berlusconi said in a rallying cry ahead of Sunday’s vote. Berlusconi initially gave his blessing to the proposed reform but he switched sides as a rising tide of opposition put Renzi’s job on the line. Thousands of supporters of a “No” vote were joined by TV crews from all over the world in Turin to hear Beppe Grillo, the comic who founded the populist Five Star Movement, give his final rallying call. Renzi meanwhile was clinging to hope of a last-minute turnaround in voter sentiment. “Never have there been so many people undecided. The referendum match will be decided in the last 48 hours,” he said, despite polls pointing to a victory for the “No” camp. Such an outcome is expected to trigger the reformist premier’s resignation after just under three years in office and plunge the country into a phase of political uncertainty. After Britain’s vote to leave the EU and Donald Trump’s presidential triumph in the United States, Renzi is being portrayed as next in line to suffer a populist backlash from fed-up and forgotten voters. His pledge to quit if he loses the vote has focused the campaign on his record and exacerbated fears of political instability and economic turbulence if he loses. At stake Sunday is whether to slash the size and powers of the second-chamber Senate and transfer other powers from the regions to the national government. Renzi says this will mean more effective leadership of a country that has had 60 different governments since the constitution was approved in 1948. As a result, it seems certain some disgruntled voters will vote “No” as a form of protest either against Renzi or over years of economic stagnation. But the proposals have also come under fire from opponents who see them as ill-considered and potentially opening the door to the kind of authoritarian rule the constitution is designed to prevent. Politically and economically, the stakes are high. Renzi sees the emasculation of the second chamber as key to ensuring difficult but necessary legislation does not get blocked or delayed in parliament while saving nearly 500 million euros ($532 million) a year in operating costs. “If you want to abolish the privileges of the most expensive political caste in the world, you have to vote yes,” the youthful premier said Friday. Opponents insist the savings will be much smaller and that the legislative gridlock problem is exaggerated: Renzi did not have any trouble getting his controversial Jobs Act through parliament last year. A “No” vote is seen as bolstering Grillo, potentially giving Five Star a platform for an assault on power nationally, as well as Matteo Salvini, leader of the anti-immigrant, anti-EU Northern League. Economically, the biggest concern is that post-referendum political instability could scupper Italy’s efforts to resolve a bad loans crisis in the banking sector and spark turmoil across the eurozone.