Michelini was born in Florence. An accountant by profession, he was a lower to middle-ranking figure in the National Fascist Party, rising to become secretary of the party in Rome. Despite this, Michelini, a pro-Franco veteran of the Spanish Civil War, did not hold office in the Italian Social Republic.
Michelini emerged as leader of the MSI in 1954 and sought to moderate the party's neo-fascism in an attempt to bring it more into the political mainstream, an endeavour in which he largely failed. Linked to financial powers in Rome as well as the Vatican City who sought to move the MSI away from its third position rhetoric into more conservative ideals. His policies helped to push some of the more radical elements out of the party and into such fringe groups as Avanguardia Nazionale and Ordine Nuovo. Despite these attempts at moderation the MSI lost support under Michelini's dropping from 5.8% in the 1953 general election to 4.9% in the 1958 election. He nevertheless remained leader until his death when Giorgio Almirante, the head of the extremist faction, returned to the leadership.
- P. Davies & D. Lynch, The Routledge Companion to Fascism and the Far Right, 2002, p.225
- R. Eatwell, Fascism A History, 2003, p. 250
- Franco Ferraresi, Threats to Democracy - The Radical Right in Italy After the War, Princeton University Press, 1996, p. 24
- Ferraresi, Threats to Democracy, p. 53
- Ferraresi, Threats to Democracy, p. 28