Speculations over a new party led by Renzi date back to 2012, when he was defeated by Bersani in the run-off of the centre-left primary election. Rumors stopped when Renzi was elected secretary of the PD in December 2013. He also became Prime Minister in February 2014. He led the party to huge electoral success in the 2014 European Parliament election (40.8%), but badly lost the 2016 Italian constitutional referendum (59.1% to 40.9%), which caused his resignation as Prime Minister.