Lisboans cast their ballots in the Portuguese general elections on Sunday.

Current Socialist Prime Minister Antonio Costa, who is seeking re-election after coming to power in 2015, is the favourite, with the latest polls showing his Socialist Party (PS) at 36-39 per cent compared to opposition centre-right Social Democrats (PSD) at 25-30 per cent.

Several voters said they cast their vote because it's their right and duty. "I'm expecting for none of the parties to reach a majority result," one voter added. Another voter said he expected the election to change "nothing" and result in "the same thing of what we have now. Very little difference."

A win would ensure a Socialists' grasp on the country's 230-seat parliament, but Costa would still need to enter a coalition with a smaller left-wing party to govern.

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