Who is PM now and what is he known for

The current prime minister is Antonio Costa, whose center-left Socialist Party has been in power, in a pact with the Communists and the Left Bloc since shortly after the inconclusive 2015 election, which had actually been topped by the centre-right Social Democrats. His platform at the time was to bring an end to the austerity which had followed the financial crisis in the country.

While populists have swept to power elsewhere, Costa's government has proved remarkably stable and kept a relatively tight grip on spending, and the Portuguese economy has enjoyed four years of growth.  Costa goes into the election with a pledge to maintain prudent management of the economy.
 

Who are the contenders in election

The latest opinion polls suggest that Antonio Costa's Socialist Party is set to top the polls in Sunday's vote, with a 37 percent share. The next highest party in the polls is the center-right Social Democrats, led by Rui Rio, with 30 percent. Neither of those is enough to provide a majority government, so both would be expected to have to work with other parties to form a government.

Those other parties include the Communists - with six percent in the poll - and the Left Bloc, led by Catarina Martins, with a 10 percent share of votes according to the poll by Catolica University pollsters for Publico daily and RTP television. Both parties have worked with Costa since 2015 but there have been differences with the Left Bloc during the campaign.

The wildcard in this year's election could be the People-Animals-Nature party, with their vote share up to three percent, which could bring them four seats, with it doing well among younger voters.

Leader Andre Silva says his party is not focused on left and right - but will back a government if it commits to changing "our productivist, oil-dependent, highly carbonized economy."

How is the Portuguese economy doing

The financial crisis hit Portugal hard, slashing 700,000 jobs from the economy between 2008 and 2013, causing the unemployment rate to rise as high as 17 percent.

It required a bailout from the EU and the International Monetary Fund, which was only completed in 2014 after a series of harsh austerity measures were introduced. 

Since then, the economy has been bouncing back, with Costa presiding over a growing economy for  the past four years and an unemployment rate which is now down to seven percent, a 14-year low. But, according to the OECD, there is still wide inequality.

What are the main issues?

There are several other issues this time round in addition to the state of the nation's finances - and the environmental issues already mentioned.

Most notably, it remains to be seen what the impact will be of the troubles faced by former Socialist Party defense minister Azeredo Lopes, who denies an alleged role in a suspected army cover-up of a theft of weapons.

However, given the country's experience of economic turmoil, it is likely to be the economy, and who voters most trust with it, that will prove the key issue on Sunday.

Ruling Socialists lead in Sunday's election in Portugal but far from the desired majority