Il Nuovo Postiglione - Nationalist victory spells trouble for Poland's Tusk

Nawrocki, who is supported by the former governing Law and Justice (PiS) party, is a fierce opponent of Polish Prime Minister Donald Tusk, who is a former European Council chief.

His aim to strengthen ties with US President Donald Trump could also limit the Tusk government's room for action on foreign policy, experts said.

"Nawrocki's main task will be to bring down the government of Donald Tusk, regardless of the cost," Wojciech Przybylski, head of the Res Publica foundation, told AFP.

He said Nawrocki's aim would be to bring about "early elections, or at least a serious crisis" to usher in a government led by the populist PiS, Poland's main opposition force.

The expert predicted that existing divisions within the ruling coalition, particularly between Tusk's Civic Coalition (KO) and the conservative PSL farmers party, would increase.

Piotr Buras, head of the Warsaw office of the European Council on Foreign Relations, a think tank, agreed that Nawrocki's presidency would be a "rough ride" for Tusk.

He called the result of the vote -- 51 percent for Nawrocki and 49 percent for liberal rival Rafal Trzaskowski -- a "yellow card" from Poles for Tusk's government.

"Dissatisfaction with Tusk's government was the main reason for Trzaskowski's defeat," he said, pointing to the large number of young voters who cast their ballots for Nawrocki.

- 'Serious escalation' -

Polish presidents have a five-year mandate and influence over foreign and defence policies but their key power is to be able to veto legislation from the government.

Several reforms proposed by Tusk have been blocked by an impasse with the outgoing president, Andrzej Duda, who is a Nawrocki ally.

Buras said he believes that Nawrocki's views are "far more radical and right-wing" than those of Duda and that once he takes over in the coming weeks "no major reform project... will be possible".

He mentioned specifically government proposals on introducing legislation allowing same-sex unions and easing Poland's near-total ban on abortion.

Nawrocki's aim will be to undermine the government "and prepare the ground for the return to power of PiS".

He predicted "a very serious escalation of the political conflict in Poland".

"It has always been polarised for many years but this will intensify," he said.

In terms of foreign policy, Nawrocki's alignment with Trump and his MAGA-style stance could spell changes, he said.

Tusk's promotion for "a stronger European defence policy" and Poland's support for EU and NATO accession for neighbouring Ukraine "could be seriously hampered", Buras said.

Nawrocki has been critical of Ukraine and its president, Volodymyr Zelensky, and wants to reduce benefits for the estimated one million Ukrainian refugees in Poland.

But Przybylski said Poland's increasingly powerful role within the European Union was unlikely to change with the new president.

He predicted, however, that growing political tensions will not allow Poland to "fully realise the potential that we have".

M.Dodaro--INP