For the first time in modern Spanish history, four parties are vying for votes in yesterday's polls - not just the usual Socialists and Conservatives - after the emergence of new political forces.
The 60-year-old incumbent conservative Prime Minister Mariano Rajoy is asking Spaniards to re-elect him, positioning himself as the safe pair of hands who has saved the country from economic collapse and put it on the path of recovery.
Elected in 2011, the Popular Party (PP) chief put in place a series of drastic, highly unpopular austerity measures but says "the worst of the crisis is over" and has promised to create two million jobs over the next four years.
Straight-laced, sedate - even boring, some say - Mr Rajoy started out as a land registrar but quickly embraced politics, joining the Popular Alliance, the party founded by ministers of former dictator Francisco Franco which later became the PP.
Faced with much younger rivals, the grey-bearded, bespectacled premier from the conservative north-western region of Galicia points to his 34 years in politics as a badge of experience.
Nicknamed "El Guapo" - "Mr Handsome" - the 43-year-old economist from Madrid was unknown to the public two years ago, before being elected to head and renovate the troubled Socialist party E last year.
The Socialists were turfed out of power in a crushing November 2011 election defeat, seen as punishment for a recession, mushrooming debt and sky-high joblessness.
The former university basketball player has cultivated a down-to-earth image in his bid to turn around his party's flagging fortunes before the elections.
He has promised a "minimum living wage for families without resources" and to reinstate the health rights of workers, immigrants and women that he says have been trampled on by the PP.
Known for his easy-going style, the pony-tailed 37-year-old is the head of the anti-austerity Podemos, which rose to prominence two years ago on the back of the "Indignados" protest movement against growing inequality, spending cuts and corruption.
The former politics professor was elected to the European Parliament last year, where he stayed for 14 months before throwing everything into the current election race.
A fervent critic of Brussels' austerity measures, he has also blasted repeated corruption scandals at the PP and Socialist party, and defends "the lower classes" for whom he wants "an emergency social plan." His party - an ally of Greece's radical ruling Syriza party - vaunts the fact that mayors in the three major cities of Madrid, Barcelona and Cadiz all emerged from the "Indignados" movement.
He is the youngest of the four and heads the centrist Ciudadanos, which has experienced a spectacular rise in popularity due to its stance against corruption and in favour of independence in the Catalonia region, where it hails from.
The 36-year-old lawyer from Barcelona has devoted the past eight years to politics.
A brilliant, telegenic orator and an adept of social media, he was a lawmaker in Catalonia's regional Parliament between 2006 and 2015.
Promoting "reasonable change", his party - which emerged in 2006 but only reached the mainstream this year - is liberal on the economic and social front.
It wants to invest more in research and education, and create a single employment contract system to try and iron out differences between those in stable jobs and others in precarious positions.