By Gavin Jones and Angelo Amante
ROME (Reuters) - Italy's rightist bloc led by Giorgia Meloni is strongly expected to win Sunday's election but voter sentiment has shifted in the last two weeks and surprises should not be ruled out, pollsters say.
Since publication of opinion polls was banned two weeks ago the left-leaning, unaligned 5-Star Movement appears to have made significant progress while the rightist League is struggling, according to seven pollsters interviewed by Reuters.
Matteo Salvini's League is the main ally of Meloni's Brothers of Italy party, which has probably consolidated its position as the most popular force ahead of Enrico Letta's centre-left Democratic Party (PD), the pollsters said.
In terms of the overall result, most said the probability the right will win a majority in both houses of parliament and form the next government has declined somewhat due to 5-Star's rise, but it remains by far the most likely outcome.
"Nothing should be ruled out," said Renato Mannheimer, head of the Eumetra polling agency. "I would put the likelihood of a rightist majority at 60-65%, which has shrunk from about 80% three weeks ago."
All the other pollsters saw less chance of an upset. Their estimates on the probability of a conservative win ranged from 70% right up to 100% forecast by Federico Benini, head of the Winpoll agency.
At the time of the poll blackout on Sept. 10 most surveys put Brothers of Italy at around 24% and the combined conservative bloc -- also comprising the League and former premier Silvio Berlusconi's Forza Italia -- on about 46%.
Its victory was considered assured because of divisions on the left, in particular the collapse shortly before campaigning began of an alliance between the PD and former Prime Minister Giuseppe Conte's 5-Star Movement.
That rightist victory scenario remains firmly in place, the pollsters said, despite the signs of progress for 5-Star which was in deep crisis until a few months ago but is now widely expected to leapfrog the League as the third most popular party.
Conte has moved 5-Star to the left and seems to be reaping the rewards of a campaign focused on vigorously defending its flagship "citizens' income" poverty relief scheme whose beneficiaries are concentrated in southern Italy.
"Conte has run a very good campaign and has hardly put a foot wrong," said Fabrizio Masia, head of the agency EMG Different.
Nonetheless, most pollsters agreed the split between 5-Star and the PD will wreck both parties' chances in the third of the parliamentary seats assigned by a first-past-the-post system. These are seen going almost entirely to the united right.
The rest of the seats are allocated by proportional representation.
"Even the growth of the 5-Star, unless it is phenomenal growth, appears insufficient to prevent the centre-right from winning," said Lorenzo Pregliasco, head of the YouTrend agency.
Masia said the conservatives could only be stopped by a 5-Star "surge" coupled with a jump in support for the centrist "Action" party to about 10%, stealing votes from the right. Before the polls were suspended, they had Action on around 6.5%.
(Writing by Gavin Jones; Editing by Toby Chopra)