The Socialists and the far-left Unidas Podemos together would have up to 153 seats, compared with the 165 that they received in April.
Spain's second national election this year will not give the ruling Socialists the boost in seats they were hoping for and will do nothing to solve a political stalemate, a poll of polls compiled by newspaper El Pais indicated Wednesday.
The inconclusive result in April triggered a months-long political impasse.
Socialist leader Pedro Sanchez last month called a fresh election for Nov. 10 after refusing to strike a coalition deal with the far-left Unidas Podemos, betting that the repeat ballot would put his party in a better position.
But although his Socialist party is poised to come first, it will be with fewer votes than last time and garnering just two more seats, according to the new survey - far from a majority or the boost initially predicted by opinion polls.
Wednesday's El Pais compilation of the countries' main polls suggested that the Socialists would win 27.8 percent of the vote, or 125 seats in the 350-seat parliament.
In April, the Socialists received 28.7 percent of support and 123 seats, far short of the 176 seats needed for a majority government.
The survey showed Vox, the far-right party that entered parliament for the first time in April, could overtake the liberal Ciudadanos to become the fourth-strongest party, with 10.5 percent of support and 33 seats, the poll of polls suggested.
Pollsters have been finding it hard to predict the far-right party's votes. In the lead up to April's election, some suggested a similar result for Vox, but ultimately the party's anti-immigrant and nationalist messaging earned 24 seats.
The El Pais survey saw the conservative People's Party winning up to 96 seats.
The remaining votes are likely to be fragmented between the new political forces that have erupted since the financial crisis and regional parties.
Less than a month before the country's fourth national election in four years, the polls showed little hope for breaking the stalemate that has characterized Spanish politics.
The Socialists and the far-left Unidas Podemos together would have up to 153 seats, compared with the 165 that they received in April, forcing the Socialists to rely on regional parties, including pro-independence ones from Catalonia, to form a government.
Left-wing newcomer Mas Pais (More Country), a spin-off of Podemos, would earn as many as eight seats.
A coalition of parties on the right, from the People's Party to Ciudadanos and Vox would also fail to reach a majority, with 150 seats between them.
The current crisis in the northeastern region of Catalonia, where Madrid is facing pro-independence protests, could also have an impact on the election.