ONE word can make all the difference. For the Italian left it was Chi? (Who?). On January 4th Matteo Renzi, the new leader of the centre-left Democratic Party (PD), was asked about a suggestion by the deputy finance minister from the PD, Stefano Fassina. “Chi?” was his contemptuous reply. Mr Fassina promptly resigned.Thus began a difficult few days for the Italian left (Mr Renzi’s predecessor, Pierluigi Bersani, later went to hospital after suffering a cerebral haemorrhage). Mr Fassina mattered more than most ministers, as keeper of the PD’s left-wing conscience and an influence over the economic policy of Enrico Letta’s left-right coalition. His departure reveals the tensions in the PD caused by the election of the business-friendly Mr Renzi in December.Like many of his generation, the 38-year-old mayor of Florence despairs of Italy’s political establishment. Ignoring the PD old guard as well as younger associates like Mr Fassina, he has formed an executive composed entirely of his own allies. Mr Fassina’s resignation was largely ideologically motivated. But, as he told an interviewer, it was also no fun being in a government under constant attack from Mr Renzi, leader of the main party ostensibly supporting it. Mr Fassina’s suggestion, which prompted Mr Renzi’s caustic Chi?, was for a reshuffle so…