By Barry Moody

ROME (Reuters) - Italy's politicians on Tuesday stepped up their campaigns in the last few days before next weekend's election with the outcome deeply uncertain and up to a third of voters still up for grabs.

Opinion polls on party standings are banned in the last two weeks before the February 24-25 poll but one of Italy's leading pollsters, Renato Mannheimer, said 27.7 percent of Italians were still undecided or could abstain.

This makes the final few days of campaigning crucial for an election which has the potential to again destabilize the euro zone. Italy came close to a major debt crisis in November 2011 before Silvio Berlusconi stood down and was replaced by technocrat Mario Monti.

Mannheimer said in the Corriere della Sera daily that about 5 million people, or 10 percent of voters, would decide in the last few days.

Political leaders were all out on the dustings in a final drive for votes with Berlusconi basking in the adulation of the party faithful in a rally in Milan on Monday night and both anti-establishment leader Beppe Grillo and outgoing premier Monti campaigning on Tuesday night.

A succession of corruption scandals over recent weeks has boosted Grillo, a Genoese comedian famous for obscenity-laced rants against a widely detested political class.

His rise has increased uncertainty over the result although experts say Berlusconi may be the biggest loser from the surge by Grillo's 5-Star Movement.

Latest estimates say he could get as much as 20 percent of the vote, way ahead Monti who has failed to gain traction at the head of an uninspiring centrist coalition which is stuck below 15 percent.

Although pollsters believe the centre-left has maintained a lead of around 4-5 points over Berlusconi's centre-right since the last polls on February 8, they are widely predicting an inconclusive result in the Senate.

The most likely outcome is that centre-left leader Pier Luigi Bersani will be forced into the arms of Monti in order to win control of the Senate, which has equal law-making powers with the lower house.

FEAR OF GRILLO

Stefano Fassina, a top official of the Democratic Party, which dominates the center-left coalition, said on Tuesday their biggest fear was that Monti would fall short of the votes needed to ensure Senate control because of Grillo's rise and a resurgence in the last month by Berlusconi.

But he added: "Our feeling is that with Monti we will have a majority in the Senate large enough to have a stable government, this is what we understand from the latest polls."

Fassina dismissed fears that Monti would refuse to join an alliance with the center-left which includes the leftist SEL party led by the openly gay governor of the southern Puglia region, Nichi Vendola.

Although Monti, struggling to build votes as a separate centrist offering, reiterated on Tuesday that he had nothing in common with the center-left, Fassina said in the end he would have to join a coalition in the interests of stability after the election. Continued...