Earlier in the week, Vittorio Feltri, the editor of Il Giornale, the newspaper controlled by Berlusconi's brother, gave a rare criticism of the prime minister, calling him "tired and confused."

On Monday, best-selling author and anti-Mafia activist Roberto Saviano told a national television audience that Berlusconi and his allies were helping the Mafia grow in power after a generation of decline.

And on Thursday, the Italian constitutional court announced it would rule on the legality of the law Berlusconi passed in 2007 to guarantee immunity from criminal prosecution for himself and a handful of other top-level government leaders.

The outcome of the next round of elections could depend more on which blocs ally themselves with others than with Berlusconi's popularity.

The IPR poll, which indicated that 28.5 percent of Italians would vote for Berlusconi, also showed 12.5 percent would vote for the Northern League, a key Berlusconi supporter.

Gianfranco Fini and Pier Ferdinando Casini, both former Berlusconi allies, polled at between 5 percent and 6 percent, with several smaller centrist and right-of-center parties under 3 percent.

That meant it remains possible that Berlusconi could manage to cobble together enough support to form a new government, especially if he and his allies manage to exceed expectations at the polls.

Another possibility would be the creation of a centrist alliance led by Fini, Casini, plus former Rome mayors Walter Veltroni and Francesco Rutelli (who have a combined 26 percent support level) and some smaller centrist parties.

A wildcard in that scenario could be Luca Cordero di Montezemolo, the president of Ferrari and one of the architects of the dramatic turnaround of Italian carmaker Fiat.

Cordero di Montezemolo, 63, has no previous political experience but in recent days the Italian press has speculated that he could use his high profile in business as a springboard into politics the way Berlusconi did in the early 1990s.