After voting, Berlusconi described the topless protesters as "an exaggeration. There are situations that are outside the bounds of reason, and we can't do anything about them," he said.
While a man of the left, Bersani has shown himself to have a surprising amount in common with the center-right Monti -- and the two have hinted at the possibility of teaming up in a coalition. Bersani was Monti's most loyal backer in Parliament during the respected economist's tenure at the head of a technocratic government. And in ministerial posts in previous center-left governments, Bersani fought hard to free up such areas of the economy as energy, insurance and banking services.
But it's uncertain that Monti will be able muster the votes needed to give Bersani's Democratic Party a stable majority in both houses of Parliament.
"Forming a government with a stable parliamentary alliance may prove tricky after elections," said Eoin Ryan, an analyst with IHS Global Insight. "A surge in support for antiausterity parties is raising chances of an indecisive election result and postvote political instability."
Another factor is turnout. Usually some 80% of the 50 million eligible voters go to the polls, but experts are predicting many will stay away in anger, hurting mainstream parties.
Interior Ministry figures put turnout by 7 p.m. at 44%, 2.5 percentage points less than in the last national elections in 2008.
Italian elections are usually held in spring, and this balloting came amid bad weather in much of the country, including snow in the north. Rain was forecast for much of the country Monday.
When Berlusconi stepped down in November 2011, newspapers were writing his political obituary. At 76, blamed for mismanaging the economy and disgraced by criminal allegations of sex with an underage prostitute, the billionaire media baron appeared finished as a political force.
But Berlusconi has proven time and again -- over 20 years at the center of Italian politics -- that he should never be counted out.