One speculation as to why Sánchez has called an election in the middle of the holiday is that he fears that the left-wing coalition he has worked with would grow stronger and become a real contender, if the election is not held until December.
Trans issues are at the center
The issues at the top of the voters' agenda are values issues.
"Among other things, it's about trans people's rights, there's been a lot of talk about abortion and how to relate to immigration," says Regina Svedberg Ågren.
Those vying for power are the two largest parties, the Social Democratic PSOE and the conservative PP. According to opinion polls, the Conservatives have a slight advantage.
"So it looks like there will be a change of government. But none of the parties seem likely to have a majority of their own, so there will probably be difficult government negotiations, says Regina Svedberg Ågren.
Many have voted by post
2.5 million Spaniards have already voted by post because many are on holiday.
– It is hoped that over 30 million Spaniards will go to the polls on Sunday, says Regina Svedberg Ågren.
See which parties can get a wave master role in the clip.