Surveys suggest that the outcome of today's vote will be an even more fractured lower house, with less of a difference between the left-wing and right-wing blocs.
But after an inconclusive result in April and unsuccessful coalition talks with the anti-austerity Podemos, which now seems to be shedding support, Sánchez again looks unlikely to win enough seats to be able to form a left-leaning government.
In the breakaway region, where the build-up to the election has been marked by massive and sometimes violent protests at prison sentences handed down last month to nine independence leaders, Catalan President Quim Torra also made an appeal for "a massive turnout". But the conservative People's Party is taking a tougher approach.
Julia Giobelina, 34-year-old web designer from Madrid, was angry at having to vote for the second time in less than seven months, but said she cast her vote at the Palacio de Valdés public school in central Madrid in the hope of stopping the rise of Vox.
Spanish acting Prime Minister and Socialist Workers' Party (PSOE) leader Pedro Sanchez takes a selfie with a supporter during a campaign closing rally ahead of general election, in Barcelona, Spain November 8, 2019. "We think that combining the courage of United We Can and the experience of the Socialist party we can convert our country into a reference point for social policies", Iglesias said Sunday.
Spain, a country which returned to democracy after a near four-decade right wing dictatorship under late Gen. Francisco Franco, used to take pride in claiming no far-right group had seats in the national parliament, unlike the rest of Europe. But if the conservatives and Vox increase their number of seats in the Parliament, the relationship with Catalonia is certain to become more hard.