A day after Miss Spain Mireia Lalaguna Royo was crowned Miss World 2015, millions of Spaniards are heading to polls to seal the fate of the European nation in the coming years. With the country's traditional two-party system being put under threat, the parliamentary elections are said to be the most hotly-contested polls in recent history.

This is the first time outside parties are entering the race since the inception of democracy in Spain – after dictator Francisco Franco's rule ended in 1975 – in the competition for power. The ruling Popular Party (PP) and Socialists are facing fresh salvo from the newly-inducted anti-austerity Podemos and the centre-right Ciudadanos (Citizens).

Voting begins at 9am local time with polls predicting a marginal lead for Prime Minister Mariano Rajoy's conservative party, which is seeking a fourth term in office. Spaniards will cast ballot in one of the most unpredictable elections in the country's recent history amid a barrage of economic woes and spiralling allegations of corruption in the political system.

Nearly one-third of the 36 million voters are undecided on whom they would choose, according to preliminary polls. "The truth is I don't really know [what's going to happen]. I think they'll have to form a coalition. But I don't know who will form a coalition with who," a woman named Valencia told Euronews.

One of the possible outcomes could be that the ruling PP would form a coalition with other parties if they win, but do not secure an absolute majority. Nevertheless, political analysts are certain that the election results would put an end to the two-party system in Spain.

"I'm convinced that Spaniards will ask for change. I'm convinced that these years of weariness, of corruption ... are coming to an end," Ciudadanos's leader Albert Rivera told reporters in Madrid during his campaign rally on 18 December in the run up to the polls.

Podemos' Pablo Iglesias, a 37-year old university lecturer, has also been trying to ride the anti-government wave over austerity programmes. Urging his supporters, he said: "We're ready to lead a new transition in this country. This is the moment that all the difficulties and obstacles they've put in our way start to make sense, because we've made it to the end of the campaign with the possibility of winning."

Both newcomers are vying for a third spot in the elections, eventually playing kingmaker on who will come to power. Analysts have also warned an unstable coalition government would worsen the financial hardships for Spain, EU's fifth largest economy.