Guido Moltedo, a political commentator from the Italian Europa newspaper, told Al Jazeera: "These are local elections, but they have been transformed by Berlusconi into a referendum on his government."
In February, members of Berlusconi's People of Freedom (PDL) party were arrested after being accused of accepting kickbacks.
That scandal was quickly followed by embarrassment when PDL fumbled over its candidate lists in Rome's Lazio region and Berlusconi's native Lombardy.
The PDL was left off the ballot sheet in the Rome province - which has around 3.4 million voters - after it failed to register in time.
Berlusconi responded by accusing "communist" magistrates and the opposition of trying to influence the vote.
Surveys published before a two-week blackout around polling indicated that this could tip the balance in favour of the centre-left in Lazio and weigh on the overall turnout.
Earlier this month, prosecutors opened an investigation into allegations that Berlusconi, 73, tried to gag a political talk show that is often critical of him.
National broadcasters suspended their political programming ahead of regional elections, saying they did not want to be seen favouring any one party, but also to avoid fines for bias.
Rai television, which groups all public channels, was still not able to avoid a fine however, when its main television news programme was hit with a €100,000 euros ($134,000) penalty for "imbalance" in reporting and "weak" coverage of the smaller candidates.
Balance of power
Concerns over the euro zone's third largest economy, reeling from its worst post-war recession, are likely to weigh on the vote - the last test at the ballot box for the conservative leader before his third term ends in 2013.
Pollsters say rising unemployment is the main concern for 79 per cent of Italians now, compared with 47 per cent in 2008.
Polls issued before the publication ban came into force pointed to the centre-right retaining control of Lombardy and Veneto regions in the north and winning over Calabria and possibly Campania in the south.
The centre-left is seen holding on to at least five regions, four of them in its traditional central heartland - Emilia Romagna, Tuscany, Umbria, Marche - and Basilicata in the south.
Four regions - including Piedmont and the key Lazio region which contains Rome - are too close to call.
James Walston, a political science professor at the American University of Rome, said: "These elections are very important to give a feel of the support Berlusconi has in the country, and the relative power of the different parties in his coalition.
"The results will be more confused [than usual] because in Rome we don't have the main government party running, so that will be a big excuse," he said.
A poll for the Corriere della Sera newspaper said the government's approval rating had fallen to 39 per cent while 17 per cent of voters had decided not to vote or to change their vote as a result of the pre-election chaos.
Analysts say that recent scandal may alter the balance of power within Berlusconi's coalition, with the Northern League expected to win votes in the rich, industrial north at the expense of Berlusconi's own PDL.
Umberto Bossi, the Northern League party leader, said in an interview last week that it would be "fairly logical" for the anti-immigration party to do better than the PDL in Veneto and Piedmont and to make gains in Lombardy.
A strong showing would increase its weight within the government, and in turn weaken Gianfranco Fini, the lower house speaker often tipped as a possible successor to Berlusconi.
Fini, whose southern-based National Alliance merged with Berlusconi's party last year, has been increasingly critical of the government, and there is some speculation that he may decide to recreate his own political force.
In the lead up to the election, Italy's postal service intercepted a threatening letter containing a bullet addressed to Berlusconi, police said on Saturday.
A large envelope containing the threat "you will end up like a rat" was discovered on Friday in a post office in the Libate suburb of the northern city of Milan, police said. Berlusconi was in Libya for an Arab League summit.