Silvio Berlusconi's center-right coalition is leading in a vital battleground region ahead of next month's Italian election, making it harder for left-wing rivals to form a stable parliamentary majority, according to a poll on Sunday.
Whoever wins the February 24-25 vote will have to tackle a deep recession and rising unemployment in the euro zone's third-largest economy as well as keeping strained public finances under control.
If the result in the northern region of Lombardy were confirmed, it could increase the chances of a post-election deal between the center-left Democratic Party (PD), which is leading in national opinion polls, and outgoing Prime Minister Mario Monti's centrist formation.
According to the survey in Sunday's Corriere della Sera, the alliance of Berlusconi's People of Freedom (PDL) party and the pro-devolution Northern League had 35.7 percent support in Lombardy, home to Italy's financial capital Milan.
The center-left bloc made up of the PD led by Pier Luigi Bersani and its leftist allies had 32.3 percent support, the poll by the respected ISPO institute showed.
The poll is important because Lombardy has more seats in the 315-member Senate than any other region and is thus one of the keys to control of the upper house.
The bitter experience of the last center-left government under Romano Prodi, which collapsed less than halfway through its term in 2008 because its wafer-thin Senate majority disappeared, underlines the importance of the race.
The PD is expected to win control of the lower house of parliament, helped by a complicated electoral system that guarantees the biggest party a 54 percent majority of seats, but the Senate race is decided by separate battles in each region.
The PD has pledged to stick to public finance targets that Monti has agreed with Italy's European partners and says it will maintain his broad reform course if it wins the election on February 24-25, but wants greater emphasis on social justice and growth.
Monti has criticized some elements of the left as hostile to reform, prompting increasingly acerbic responses from Bersani and other center-left leaders, but relations between the two sides have been much more cordial than those with Berlusconi.
Neither side has said openly that it would form an alliance if the center-left cannot control the upper house and many on the left are deeply opposed to Monti's austerity policies.
But failure to gain outright control of the Senate would leave Bersani with little choice.