The results of the opinion poll, published shortly after the vote at 19:00 GMT, showed no clear advantage for either the left or right bloc, indicating an impasse that could make the attempt to fail again. to form a functional government.
PSOE is expected to win 114-119 seats, down from 123 it won in the April ballot and away from the 176 parliamentary majority.
Also, the far-right party Vox would double its parliamentary representation, from 24 to 56-59 seats. This party, which entered parliament in April, is seen as the main winner of the ballot.
The People's Party (PP) would get 85-90 seats, up from the 66 won in April.
Projections show that the left-wing United Podemos would gain 30-34 seats, down from the 42 it had, and Ciudadanos, a liberal party that opposes the secession of Catalonia, would get only 14-15 seats, a fall drastically compared to the 57 who returned to the polls in the spring.
The turnout was lower than in April.
Politically paralyzed, Spain returned to the polls for the fourth time in four years, in a context of open crisis in Catalonia that seems to have given new impetus to the far-right party Vox in a country where the far-right was marginal. since the end of Franco's dictatorship in 1975.