The center-left is on course to win Italy's election despite a remarkable surge by Silvio Berlusconi, but it is likely to have to form a governing coalition with outgoing premier Mario Monti, final polls before the Feb 24-25 vote showed on Friday.
Most polls published before a pre-vote blackout showed Pier Luigi Bersani's center-left still five or more points ahead, despite a scandal over a Tuscan bank with which it has links and a continuing fight-back by former Prime Minister Berlusconi.
An average of polls calculated by Reuters showed Bersani on 34.7 percent, 5.7 points ahead of Berlusconi. The anti-establishment 5-Star Movement of comedian Beppe Grillo was running third on 16 percent, with Monti's centrists trailing on 13.6 percent.
While this lead is expected to give Bersani a clear majority in the lower house, the situation in the Senate is much more uncertain and most pollsters believe the center-left will need to seek an ally to govern, with Monti by far the most likely.
Senate seats are awarded by region, with a big bonus for winners. In the key battlegrounds of Sicily and Lombardy there was less than a 3 point difference between the center-left and center-right, barely above the margin of error, ISPO pollsters said in a survey for Corriere della Sera newspaper.
SWG pollsters also showed a Senate projection in which Bersani would win 146 seats, 12 short of a majority, with Monti taking 21. Such a result is considered almost certain to push Bersani into the arms of Monti, despite the former European Commissioner's lack of traction in the campaign.
"An alliance has already been made between Monti and Bersani; it is all organized," said Rome resident Luigi Jervolino as he sipped coffee in a central bar.
The Senate has equal powers to the Chamber of Deputies, and Berlusconi's target is to take enough seats to make a Bersani government unstable.
"Monti's presence in the government would mean a reliability in Europe, reliability in the markets, and a much greater strength for the government," Professor James Walston of the American University in Rome told Reuters.
Bersani and Monti have begun making cautious overtures to each other this week, but any alliance is strongly opposed by an existing member of the center-left coalition, the Left Ecology and Freedom party (SEL). Monti has called on Bersani to dump SEL or risk spooking markets.
Billionaire media magnate Berlusconi, a master communicator, has sharply eroded the center-left's lead in the last month, promising sweeping tax cuts, while a scandal over murky derivatives deals at Monte dei Paschi bank has hurt Bersani's Democratic Party because of its local links with the Tuscan lender.
After diving into the campaign in December, with his party close to disintegration and behind Grillo on around 15 percent, Berlusconi has gained around 5 points for his People of Freedom (PDL) group with a blitz of television appearances that have eclipsed the uncharismatic figures of Monti and Bersani.
But most experts believe it is too late for him to catch up after a shorter than usual election campaign, and many Italians are skeptical of his promises to pay back a hated housing tax and create 4 million new jobs.
The Roman Catholic Church, once a supporter of Berlusconi, has abandoned him after a string of scandals, instead backing the devout Monti.
"Italians will no longer be taken for a ride by anybody or anything," said Cardinal Angelo Bagnasco, head of the Italian Church.
Berlusconi, weakened by a lurid sex scandal, stepped down in November 2011 as Italy teetered on the brink of a Greek-style debt crisis. He was replaced by technocrat Monti, who restored Italy's reputation in the markets and helped bring its borrowing costs under control.
But as a candidate, Monti has failed to meet the expectations of investors and foreign governments that he could lead a radical renewal in Italy, with his centrist group stuck behind Grillo on less than 15 percent.
Pollsters were divided on whether much could change between now and the election. Renato Mannheimer, head of Ipsos, said Friday's polls were only a starting point, given that undecided voters made up around a third of the total.
But Roberto Weber, head of SWG and Nicola Piepoli, head of a firm with the same name, both said the situation had stabilized.
"It won't change ... The polls will not move anymore," Piepoli told Reuters.
"I expect the gap (between the parties) today to be confirmed after the vote," said Weber.
Piepoli believes the undecided voters will be evenly distributed between the parties, with the possibility of a slight increase for Grillo, whose anti-establishment party looks like getting around 80 seats in the house and 39 senators, according to the SWG projection.