ROME (Reuters) - The center-left is on course to win Italy's election but it may have to form a coalition with outgoing premier Mario Monti, final polls before the Feb 24-25 vote showed on Friday.
Polls published before a pre-vote blackout mostly showed Pierluigi Bersani's Democratic Party still five or more points ahead, despite a scandal over a bank it is linked to and former Prime Minister Silvio Berlusconi's continuing resurgence.
Pollsters said a large group of undecided voters meant much could change in the final two weeks, but most polls confirmed predictions that Bersani would fall short in the Senate and need an ally to govern, with Monti by far the most likely candidate.
Bersani looks guaranteed of a healthy majority in the lower house, where he only needs to be ahead to win a hefty bonus of seats.
An ISPO poll for Corriere della Sera newspaper showed the center-left on 37.2 percent, against Berlusconi's center-right on 29.7 percent.
But Senate seats are awarded by region, and 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 said.
The Senate has equal powers to the Chamber of Deputies in making laws.
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 international investors.
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 derivatives losses at Banca Monte dei Paschi di Siena has hurt Bersani's Democratic Party, which has historical links with the Tuscan lender.
A Demos and Pi poll in left-leaning daily La Repubblica showed Bersani's coalition on 34.1 percent, having lost 4 points in three weeks. In the same period Berlusconi's group surged to 28.6 percent from 25.8.
The 5-Star Movement of comedian Beppe Grillo also gained ground, to 16 percent from 13 percent. Monti's centrists were on 16 percent, with little change from three weeks earlier.
(Reporting by Naomi O'Leary; editing by Barry Moody and Philippa Fletcher)