Caretaker Prime Minister Pedro Sánchez of the Socialist Party has urged citizens to go to the polls and vote in order to “strengthen democracy”
According to the early results the Socialists are set to win 131 seats while their former coalition partner Podemos would have 39.
There are 36.8 million eligible voters, and the outcome will largely hinge on how many political abstainers decide to go vote on a clear a sunny day when the weather is no excuse to stay home.
Spain's prime minister faced an onslaught of criticism Monday from his right-wing rivals over Catalonia's secession crisis in a testy four-way debate ahead of elections, while he warned them against cozying up to the far-right.
Thousands are in central Madrid for a protest by centre-right parties opposed to a plan by the Spanish government to ease tension in the Catalonia region.