By Philip Pullella
ROME (Reuters) - Italians began voting in four referendums on Sunday that could strike a new blow against Prime Minister Silvio Berlusconi, who is still stinging from heavy local election losses last month.
The center-left opposition has been leading a spirited campaign to get voters out to cast their ballots on the questions, which concern the privatization of water utilities, nuclear energy and whether government ministers can be exempt from attending trials against them.
A central issue will be whether enough voters turn out to ensure the necessary quorum of 50 percent plus one vote. But if they repeal existing laws by voting yes, the result will likely have repercussions on his fractious center-right coalition.
"Behind the numbers lies the political fate of those who have taken a stand," Il Sole 24 Ore, Italy's leading business daily, said on Sunday.
"It's clear that a wave of 'yes' votes will result in a shock, perhaps the final one, for his (Berlusconi's) premiership and even for his leadership of his party," the paper said.
At 1700 GMT on Sunday, nearly 30 percent of eligible voters had cast ballots, which gave the opposition encouragement that the quorum would be reached by Monday afternoon -- when the two days of voting ends -- or even before.
A quorum would be a setback to Berlusconi because he has said he would not vote and some of his ministers have urged voters to boycott.
For some, the votes will be a way to demonstrate their disappointment with Berlusconi himself, who is facing a sex scandal and three fraud trials.
If the quorum is reached, it would mean that "more than half of Italians are pointing a finger against him," Il Sole said.
The referendum on nuclear power is the most emotive of the four, in the wake of the disaster at Japan's Fukushima reactor in March. Polls say most Italians are against nuclear energy, which they consider unsafe in a country prone to earthquakes.
Berlusconi is a big proponent of nuclear power, which the center right says is indispensable for the future of a country that imports nearly all its energy.
Last year the government passed a law to re-start a nuclear energy program, which was halted in 1987 by another referendum. Aware of the likely backlash following Fukushima, the government has suspended the plans but a referendum could block atomic power for decades.
Another referendum would repeal the so-called "legitimate impediment" that allows ministers to skip trial hearings against them on if they are on government business, which Berlusconi's critics say is for his personal benefit.
Two others concern the privatization of water utilities. The government says privatization is essential to finance better services. Opponents say it would just lead to higher prices.