Soon after the Soviet revolution (1917), the Spanish political parties started polarizing, and the left-wing Communist Party (PCE) and Spanish Socialist Workers' Party (PSOE) blamed the Government for supposed election fraud in small towns ("caciquismo"), which was incorrectly supposed to have been wiped out in the 1900s by the failed "regenerationist" movement. In the meantime, spiralling violence started with the murders of many leaders by both sides. Deprived of those leaders, the regime entered a general crisis, with extreme police measures which led to a dictatorship (1921–1930) during which the Senate was again abolished.