Following Italian Prime Minister Silvio Berlusconi\'s announcement that he will resign by the end of the month, four leading candidates have emerged as potential successors. Berlusconi has said he would like Italy\'s president to call early elections and has named Angelino Alfano, a former justice minister and leader of Berlusconi\'s People of Freedom party, as his nominated candidate. But in addition to calling elections, other possible options before President Giorgio Napolitano are the widening of the current centre-right coalition or a national unity cabinet. Following are biographical details on the men in the running: -- Angelino Alfano: Alfano has been a Berlusconi loyalist ever since the tycoon entered politics in the early 1990s and has risen rapidly through the ranks, becoming justice minister and then leader of Berlusconi\'s People of Freedom party. The 41-year-old lawyer is relatively young for Italian politics and is best known as the architect of a law intended to shield Berlusconi from prosecution which was then overturned by a Constitutional Court ruling. \"He will be our candidate for premier, he\'s very good. Better than one might think, and everyone has accepted his leadership,\" Berlusconi said in an interview published on Wednesday, adding that he could help out on elections. In his speech accepting the nomination as party leader this year, Alfano called for an opening to moderate centre-right forces and defended Berlusconi but said other politicians in trouble with the law should be thrown out. With Berlusconi\'s endorsement, he could be a strong candidate in elections. -- Mario Monti: A former high-profile European commissioner with a tough reputation, the 68-year-old economist is now the director of Milan\'s prestigious Bocconi University --- considered the training ground for Italy\'s financial elite. Monti was put forward as European commissioner in 1994 by Berlusconi\'s first government and stayed on in Brussels even after Massimo D\'Alema took over as prime minister -- burnishing his image as being above party politics. Romano Prodi, a former prime minister and ex-European Commission president, gave him his blessing in an interview with La Repubblica daily on Saturday. \"Monti\'s time has come,\" Prodi said. He said Monti was important for the current debt crisis because he was \"respected in Europe and the world.\" Under Monti\'s leadership, the European Commission established a formidable trust-busting reputation taking on US giants Microsoft and General Electric. The Economist called him \"Super Mario\" -- a moniker inherited by former Bank of Italy chief and new European Central bank president Mario Draghi. Monti is seen as a leading candidate to create a technocratic national unity government. -- Gianni Letta: Berlusconi\'s cabinet secretary and loyal right-hand man for two decades, Letta was by his master\'s side throughout Tuesday -- the day that a parliamentary revolt left his centre-right coalition without a majority. The 76-year-old former cabinet minister avoids the limelight but has been credited with cultivating relations with the United States and with the Vatican in the wake of increasingly sordid revelations about Berlusconi. \"There is only one person who is indispensable in Palazzo Chigi (the prime minister\'s office in Rome),\" Berlusconi once told journalists. \"You think it\'s Silvio Berlusconi. It\'s not, it\'s Gianni Letta.\" Letta met Berlusconi over 25 years ago when he left Il Tempo newspaper and joined Berlusconi\'s television empire. Letta was Berlusconi\'s best man when he married his second wife, the actress Veronica Lario, in 1990. Letta could be the man to lead an expanded centre-right coalition. -- Giuliano Amato: A two-time prime minister with international experience, the 73-year-old has been dubbed \"Dottor Sottile\" (\"Doctor Subtle\") by the Italian press for his ability to create consensus and for his political savvy. He graduated in law at university in Pisa and went on to obtain a master\'s at Columbia University in New York. He taught constitutional law for more than 20 years in Rome before entering politics in the 1980s. Amato was a key ally of Bettino Craxi -- a former socialist prime minister who was also close to Berlusconi. He served as prime minister between 1992 and 1993 and again between 2000 and 2001. He is a member of the main opposition Democratic Party but is respected by both sides of the political spectrum and recently headed up the organising committee for celebrations for the 150th anniversary of Italy\'s unity. Amato could be the head of a national unity government.