* Predictions suggest Berlusconi cannot succeed
* Based on regional opinion poll and projections
* Sticking point could be Monti's demand for premiership
By Barry Moody
ROME, Jan 9 (Reuters) - Silvio Berlusconi has little chance of destabilising a centre-left government after Italy's February election and outgoing premier Mario Monti is the most likely to become kingmaker, one of Italy's top experts on voting trends said on Wednesday.
Political scientist Roberto D'Alimonte, a professor at the Luiss private university in Rome, said the most likely result of the election was a centre-left government strong enough to rule alone or in coalition with Monti's centrists.
This prediction may reassure investors worried by the risk that Berlusconi could play a spoiler role after the election, returning Italy to the kind of instability that forced his replacement by Monti in November 201l as Italy careened towards a Greek-type meltdown.
The centre left of Pier Luigi Bersani, which is well ahead in opinion polls, is thought certain to win the lower house. But the real battle will be in the Senate, where seats are decided on a regional basis.
Berlusconi's strategy, fortified by an electoral pact this week with the federalist Northern League, is to win enough Senate seats to prevent Bersani passing legislation.
D'Alimonte said that as things stand this is practically impossible.
Using an Ipsos opinion poll published on Tuesday from four battleground regions in the Senate race, and updated projections from a previous survey, D'Alimonte put forward 10 different scenarios in the financial daily Sole 24 Ore.
In only one of these scenarios could Berlusconi play a blocking role and D'Alimonte said this was highly unlikely.
"This means it is not credible that Berlusconi could play a decisive role in the Senate. It is Monti who could eventually hold this position," D'Alimonte said.
Bersani has said his coalition, polling at just short of 40 percent, or more than 10 points ahead of Berlusconi's centre-right, can win both houses in the Feb 24-25 vote.
However he seemed less certain in a television interview on Wednesday, and expressed concern that by entering the election Monti was helping Berlusconi.
"I want to know from Monti who he is fighting against," Bersani told Sky Italia, warning the prime minister against "opening the door to the right," and "pulling the chestnuts out of the fire" for Berlusconi and the Northern League.
Monti said later on Wednesday that it was premature to discuss alliances, and he urged the centre left to explain its approach to aspects of policy on which it seems divided, such as whether to continue on his reform course after the vote.
"In the election campaign we should focus on the problems, and alliances will come afterwards," Monti told Radio Montecarlo.
BERLUSCONI MEDIA OFFENSIVE
Berlusconi, a skilled political operator and media magnate, insists he can still win the election by clawing back a large pool of disillusioned and undecided voters, but this seems unlikely based on all opinion polls.
He has bombarded the air waves since he returned to the front line in December and boosted the centre-right's fortunes, but his coalition is still polling less than 30 percent.
There is one potential obstacle to the idea that Monti would join a coalition with Bersani. The former European Commissioner has strongly indicated that his price would be the premiership, something Bersani rejects out of hand.
However, it seems unlikely that Monti would open the door to Berlusconi by refusing to form a stable government with Bersani.
D'Alimonte's projections are based on Bersani winning 13 of Italy's 17 regions and the race being decided in four swing areas, Lombardy, Veneto, Campania and Sicily.
In what may be even more reassuring to markets, in six of D'Alimonte's projections Bersani could rule in coalition with Monti even if his leftwing allies SEL broke away because of disagreements over economic policy.
In two of the projections the centre-left could rule without Monti. "It is not in fact to be excluded that the PD-SEL coalition could win all 17 regions and then the support of Monti's list would not be strictly indispensable," D'Alimonte said.
Berlusconi's only chance is if he can prevent Monti's coalition from crossing the eight percent threshold needed to enter the Senate, which seems out of reach since his group is polling about 15 percent.
The rivalry between the two men explains both their blitz of television appearances over recent weeks and the way in which they are concentrating their fire on each other.
Bersani's centre-left says that regardless of the result it would seek support from the centrists, which is seen as a way of reassuring European partners worried that Italy could lurch to the left and undo Monti's achievements in restoring Italy's credibility after the scandal-plagued Berlusconi's exit a year ago.
Bersani's deputy, Enrico Letta, told reporters on Wednesday that their first dialogue after the vote would be with Monti. "If we win, we will ask Monti's supporters in the centre to support the Bersani government," he said.
Bersani vows to stick to Monti's fiscal rigour but to distribute the economic pain more fairly and pursue growth.
Monti, who has rapidly thrown off his technocrat clothes and dived into campaigning since he announced his candidacy after Christmas, accused Berlusconi on Tuesday of pushing Italy towards a "precipice" before he was forced out in 2011.