An exit poll in Portugal’s general election on Sunday suggested that the race was too close to call, with moderate mainstream parties apparently poised to gather the most votes amid a predicted surge in support for a radical right populist party that could place third.

The poll predicted 29-33% of the vote for the centre-right Democratic Alliance, a grouping led by the Social Democratic Party. The centre-left Socialist Party gathered 25-29%, the poll indicated.

Populist party Chega (Enough) may have got 14-17% in third place, it suggested, up from 7% at the last election in 2022, in a drift to the political right witnessed elsewhere in the European Union.

Fifteen other parties picked up the rest.

The poll by Portugal’s Catholic University was published by public broadcaster RTP and in previous elections has proved largely accurate.

The Social Democrats and Socialists have alternated in power for decades, but they have never come up against such a strong challenge from a hard-right party.

Social Democrat leader Luis Montenegro, who likely would become prime minister if his alliance wins, ruled out during campaigning the possibility of teaming up with Chega, some of whose policy proposals are unpalatable for many Portuguese.

But if Mr Montenegro is unable to assemble a majority government, his hand could be forced, leaving Chega as a kingmaker.

Chega leader Andre Ventura, a former law professor and television football pundit, has said he is prepared to drop some of his party’s most controversial proposals – such as chemical castration for some sex offenders and the introduction of life prison sentences – if that enables his party’s inclusion in a possible governing alliance with other right-of-centre parties.

His insistence on national sovereignty instead of closer European Union integration and his plan to grant police the right to strike are other issues that could thwart his ambitions to enter a government coalition, however.

Chega ran its campaign largely on an anti-corruption platform. Corruption scandals triggered the early election after former Socialist leader and prime minister Antonio Costa resigned in November after eight years as prime minister amid a corruption investigation involving his chief of staff. Costa has not been accused of any crime.

That episode appeared to have hurt the Socialists at the ballot box.