ROME — Democratic Party leader Pier Luigi Bersani will probably win Italian elections this month, while needing an alliance with outgoing Prime Minister Mario Monti to govern, the final polls of the campaign showed.

Bersani will win an outright majority in the Chamber of Deputies, as his coalition maintains an average 5.9 percentage point lead over former Prime Minister Silvio Berlusconi’s bloc, three polls published Friday show.

Still, he will fall short of a Senate majority, which could force him to team up with Monti and risk alienating ally Nichi Vendola, who labeled such a move “suicide” for Bersani’s center-left coalition.

Italian law bans polling in the final two weeks of the campaign to avoid influencing voters. The prohibition will mean that Italians won’t be able to gauge whether Berlusconi’s surge in the polls will continue in the final weeks.

He trailed Bersani by about 15 percentage points at the beginning of January. Berlusconi’s gains have rattled investors, with the country’s 10-year bond yield gaining 45 basis points in the past weeks.

All the polls today showed Bersani winning the popular vote for the Chamber of Deputies, which means he will be given extra seats through a bonus premium to grant him a majority in the lower house. In the Senate, those bonus seats are doled out in regional races, making it more difficult to build a majority.

Lacking Majority

Bersani’s bloc would get 146 senators in the Senate including 11 senators of Vendola’s Left, Ecology, Freedom party, or SEL, while Monti’s coalition would win 21 seats, SWG institute said in its poll today. Bersani would need both Monti and SEL to assemble a 158-seat majority.

Vendola opposes many of the austerity measures passed by Monti that helped tame Italy’s budget deficit and slash borrowing costs, while saddling Italy with higher taxes and the country’s fourth recession since 2001. Monti has called on Bersani to “clip the extreme wings” of his coalition in a reference to Vendola.

An agreement with centrist parties supporting the prime minister “is not possible because of the distance between the policies of the center-left and those of Monti,” Vendola said today, according to Ansa.

Former prosecutor Antonio Ingroia, who’s running for prime minister at the head of the Civic Revolution party, said today he would be open to strike a deal with Bersani after the vote if Monti is not included.

Still, both SWG and Ipsos polls show his party is polling at around 4 percent or less, well below the 8 percent threshold he needs to get seats in the Senate.