Spain's Socialists led in a poll published on Saturday with 30.3 percent of votes, equivalent to between 122 and 133 seats in the 350-seat parliament.
Spain's Socialists increased their lead in a poll published on Saturday in newspaper El Pais with 28.8 percent of votes, equivalent to 129 seats in the 350-seat parliament, but far-right newcomer Vox also gained support ahead of a general election on April 28.
In a sign of Spain's growing political fragmentation, both the Socialists and its main ally anti-austerity Podemos, and a coalition of three right-wing parties - People's Party (PP), Ciudadanos and Vox- would fall short of a parliamentary majority, according to the poll.
The Socialists' votes increased by 1.7 percentage points from a poll published by the same newspaper on March 24 and they would gain 44 new seats in parliament.
Podemos' support also grew from 12.3 percent of votes in the previous poll to 13.2 now, but they would still lose 38 seats in parliament from the previous election in 2016.
On the conservative parties' side, PP's support decreased from 19.3 percent to 17.8. The main right-wing Spanish party would have 75 seats in parliament, its worst results ever.
Centre-right Ciudadanos is also seeing its support slim, from 17.7 percent of votes in March's poll to 14.1 now. The party would still gain 17 seats in the chamber.
Vox is the only conservative party that grows in the poll, from 10.2 percent of votes a month ago to 12.5 now, equivalent to 32 seats, being the first time in nearly four decades that far-right lawmakers would be elected to Spain’s parliament.
A coalition of PP, Ciudadanos and Vox would get 44.4 percent of votes, equivalent to 156 seats, 20 seats short of the 176 needed to secure a parliamentary majority.
The Socialists and Podemos together would hold 162 seats in parliament, also below the majority threshold.
But Socialist Pedro Sanchez could be reelected as prime minister if he manages to form another parliamentary majority with the support of the array of parties, including Podemos and Catalan pro-independence parties, that backed him last June when he won a vote of confidence against PP's government at the time.
El Pais' poll was conducted by 40db with 2,000 respondents between April 15 and 18. It had a margin of error of 2.24 percentage points.