Portugal is about to go to the polls with voters set to give their verdict on four years of austerity by either re-electing the centre-right coalition that steered the country through a punishing bailout or turning to the socialists who promise to ease painful reforms.
However, neither side is likely to win an absolute majority in the 230-seat parliament following Sunday's election.
Polling stations will open at 8am (07:00 GMT), with the first results expected about 12 hours later.
Prime Minister Pedro Passos Coelho's "Portugal Ahead" coalition, which links his centre-right Social Democratic Party with the conservative Popular Party, has made a surprising comeback in opinion polls, with most putting it ahead despite overseeing harsh cuts.
The coalition, in power since 2011, has 37.5 percent support against 32.5 percent for the main opposition socialists, led by Antonio Costa, a popular former mayor of Lisbon, according to the average of the latest surveys.
"The right has recovered a part of the centre voter electorate and has succeeded in getting out its message that a return to power of the socialists would lead the country to bankruptcy, like in 2011," political analyst Antonio Costa Pinto told the AFP new agency.
Analysts warn Portugal risks a period of political instability just as it seeks to safeguard an economic recovery after emerging from a debt crisis.
"The absence of an absolute majority, along with the lack of a clear direction, could be a negative sign for markets," said Paula Carvalho, chief economist at Portuguese bank BPI.
Coelho, a 51-year-old economist, is campaigning on his record of having navigated the country safely through the debt crisis and to a return to growth last year after three years of recession.
When he came to power in June 2011, Portugal was on the verge of defaulting on its mountain of debt.
His socialist predecessor, Jose Socrates, had just asked for a $88bn bailout from the European Union and the International Monetary Fund, making it the third eurozone country after Ireland and Greece to receive a financial rescue package.
Portugal exited the bailout scheme in May 2014 but only after the government imposed harsh austerity measures and the biggest tax hikes in living memory.
The unemployment rate has since fallen to 12 percent from a peak of 17.5 percent at the beginning of 2013.
But the recovery has yet to be felt on the streets. One in five Portuguese continues to live below the poverty line with an income less than 5,000 euros per year.
Unlike neighbouring Spain or Greece, Portugal has not seen the rise of a protest party strong enough to challenge traditional parties at the polls.
While Portugal's socialists have pledged to ease back on austerity and return more disposable income to households by lowering personal taxes and reversing public sector pay cuts, the party has promised to stick to European budget rules.
To reassure voters, Costa, 54, has had to distance himself from Socrates, who served as premier from 2005-2011.
Socrates, 58, was detained in November 2014 on suspicions of corruption and money laundering and is currently under house arrest.
Costa hardened his tone in the final weeks of the campaign, saying his group would vote against the budget if the centre-right is re-elected.
Passos Coelho responded by warning that such a move could cause "instability that could lead to new elections in a very short time".
The socialists could block a minority centre-right government by joining forces with the Left Block and the communists, which together have about 15 percent support.
With apathy gripping many voters, pollsters predict the numbers opting to stay at home may even surpass the record 41.9 percent recorded in the last election.
"I don't vote any more for anyone. It is always the same parties, the same promises, and nothing changes," said Herminio Batista, a 72-year-old pensioner.