Prime Minister Silvio Berlusconi faces a knife-edge confidence vote in parliament on Tuesday that could either trigger his downfall or see the resilient Italian leader bounce back once again. Berlusconi says he is confident of winning a majority of votes despite the defection of speaker of parliament Gianfranco Fini and around 40 lawmakers from the ruling coalition earlier this year, which has led to the vote. But his opponents from the right and the left say they have the upper hand. The contest is so tight that even President Giorgio Napolitano -- who is expected to play an important role in any political deal-making after the vote -- said 'a crystal ball' would be needed to predict its outcome. Italian newspapers have been filled in recent days with reports of attempts by Berlusconi allies to 'buy' votes by offering consultancy contracts to wavering deputies and there have been some defections to the Berlusconi camp. Prosecutors have opened an inquiry into allegations of vote-buying. The 74-year-old media tycoon burst onto Italy's corruption-ridden political scene with an election win in 1994 and has gone on to win two other votes in 2001 and 2008 and serve the longest term as prime minister in post-war Italy. He has become a figure of ridicule on the international stage -- famous for his gaffes, off-colour jokes and sexual escapades -- but is still seen as a powerful player in Italy and supporters say it is too early to write him off. 'I will secure the vote of confidence,' Berlusconi said in a message to supporters on Saturday, even as tens of thousands of protesters from the main opposition Democratic Party marched in Rome to demand a change of government. Opposition leader Pier Luigi Bersani told the crowd: 'The record of these last years is disastrous. Our country had not improved at all. We have been left behind by the strong countries of Europe.' The government's current mandate only runs out in 2013. Fini's political movement, Future and Freedom for Italy, has said it expects there will be 317 votes against Berlusconi in the 630-seat lower house of parliament. The ruling coalition has said it can get 316 votes. 'The showdown between Berlusconi and Fini is in its final act. Whoever loses risks bowing out of the political scene,' L'Espresso news weekly said. Antonio Di Pietro, a former anti-corruption judge and one of Berlusconi's fiercest critics, has said the confidence vote will be 'a resurrection of democracy, of dignity and ethics in parliament and in the institutions.' But a scathing editorial in Il Giornale, which is owned by Berlusconi's family, said earlier the rebellion against the premier 'has not succeeded.' Berlusconi is expected to give a key speech about the political crisis in the upper house of parliament, the Senate, at around 0800 GMT on Monday. The confidence votes will then be held in the Senate and in the Chamber of Deputies, the lower house, on Tuesday. Berlusconi and his allies are said to have a strong majority in the upper house and the attention is mostly on the vote in the lower house. The government already won a confidence vote on September 29 when Fini and his allies voted in favour despite having announced a break with the coalition. Their stance against the government has since hardened, with Fini calling on Berlusconi to resign last month and then pulling four ministers loyal to him out of the government when Berlusconi did not step down. The political instability in a major eurozone economy has so far had little effect on financial markets used to Italian government turbulence, but Berlusconi has argued that further trouble could undermine Italy. Many analysts say that, whatever the outcome of the vote, Italy could be headed for early parliamentary elections next year since even if Berlusconi wins the confidence vote his majority would likely be razor-thin. A poll on Saturday showed that Berlusconi's party and its ally, the Northern League party, would draw 39.6 percent of the vote in any future election. The Democratic Party and its main partner, Di Pietro's Italy of Values, would garner 31.2 percent between them. Fini's Future and Freedom for Italy would win 6.9 percent. 