The elections were quickly denounced by both main opposition parties, the leftist United Democratic Left (campaigning as part of the All-Democratic Agricultural Front) and the Centre Union, who refused to recognise the result based on numerous cases of voter intimidation and irregularities, such as sudden massive increases in support for ERE against historical patterns, or the voting by deceased persons. The Centre Union alleged that the election result had been staged by the agents of the shadowy "para-state" (παρακράτος), including the army leadership, the Greek Central Intelligence Service, and the notoriously right-wing National Guard Defence Battalions, according to a prepared emergency plan code-named Pericles (Σχέδιο «Περικλής»). Although irregularities certainly occurred, the existence of Pericles was never proven, nor is it certain that the interference in the elections radically influenced the outcome. Nevertheless, Centre Union leader George Papandreou initiated an "unrelenting struggle" ("ανένδοτος αγών") until new and fair elections were held. Hence the elections of 1961 became known in the Greek political history as the "elections of violence and fraud" (εκλογές της βίας και νοθείας).