Poland's pro-European opposition seems set to oust populists, but tense days lie ahead

Poland's presumptive next leader, Donald Tusk, has urged the country's president not to frustrate the handover of power, after final results from a tight election confirmed he is on course to remove the populist ruling party from government.

Tusk's opposition Civic Coalition (KO) party finished a close second to the incumbent Law and Justice party, known by its Polish acronym PiS. But the results of Sunday's election indicated that a coalition between KO and two other pro-European groups is the only realistic combination that could gain a majority in Poland's parliament.

In a statement addressed to Andrzej Duda, Tusk said on Tuesday: "Mr President, please make energetic and quick decisions! The winning democratic parties are ready to take responsibility for governing the country. People are waiting."

Nonetheless, weeks of high-stakes negotiations to form Warsaw's next government are expected.

PiS won the biggest share of the vote with 35.38% but lost its parliamentary majority, according to official results released Tuesday by the National Electoral Commission after all ballots were counted.

The group led by Tusk, a former Polish Prime Minister and European Council President, finished on 30.7%. The close result made the centrist Third Way and left-wing Lewica parties kingmakers; both groups are resoundly opposed to the hardline PiS and have indicated they will seek to form a new coalition government with Tusk's bloc.

The situation points to an end to PiS' divisive eight-year rule, which saw a drastic overhaul of Poland's democratic institutions and grave warnings that the country was lurching towards populist authoritarianism. Tusk had promised to restore democratic norms in Poland and cooperate with Western European allies, among whom Warsaw was fast becoming a pariah.

But a nervy few weeks may lie ahead. Duda, Poland's PiS-aligned President, is expected to give the PiS every chance to form a government before turning over proceedings to Poland's new block of opposition lawmakers. Tusk must also cement an ideologically broad coalition of politicians in order to present a workable alternative.

"We will definitely try to build a parliamentary majority," incumbent Prime Minister Mateusz Morawiecki said, despite PiS seemingly having no avenues through which to find one.

According to the Polish constitution, the president must call a new parliamentary session within 30 days of the election. Then, he has 14 days to nominate a candidate for prime minister, after which the nominee has 14 days to win a vote of confidence in parliament.

PiS' only obvious potential partner is the far-right Confederation party, which turned in a poorer than expected electoral performance after a summer of gaining momentum.

Sunday's election saw a record turnout of 74%, underscoring the intense polarization that gripped Poland over recent years, as well as the high stakes of the vote.

Tusk had painted the election as a last chance to save Polish democracy. "Democracy has won," he told supporters after Sunday's exit poll pointed to the election's outcome. "This is the end of the PiS government."

His apparent success is a major political accomplishment, in a country whose public media had essentially been reformed into government mouthpieces. Despite being a veteran of Polish and European politics, Tusk was considered the outsider throughout the campaign.

"The ruling party enjoyed clear advantage through its undue influence over the use of state resources and the public media," election monitors from the intergovernmental Organization for Security and Co-operation in Europe (OSCE) said in a statement Monday.

The OSCE added that the election campaign took place on "an uneven playing field."

Now, Tusk is on the cusp of coming to power and forcing a major political turnaround in the European Union's fifth-largest country.

But Tusk would face a monumental task in reversing PiS' illiberal reforms of the country's judiciary, media and cultural bodies. In particular, a courts system that has been stuffed with PiS-selected judges could attempt to frustrate efforts to change the mechanics of the state.

He will meanwhile seek to re-establish Poland as a major player in the EU, and likely attempt to smooth over tensions that emerged between Warsaw and Kyiv over the imports of Ukrainian grain.

Tusk was heavily critical of the PiS government for allowing the grain feud to spill over last month, at a time when the ruling party were desperate to keep hold of rural voters and appeal to farmers concerned about imported grain undercutting their prices.

Despite those tensions and an upcoming period of political uncertainty, Poland will be expected to remain a resolute partner to Kyiv, particularly in relation to military supplies and humanitarian aid, as Ukraine's war with Russia grinds on.

CNN's Antonia Mortensen and Alex Hardie contributed reporting.