A proposed conservative government failed to win a majority in the Polish parliament, a widely expected outcome that paves the way for Donald Tusk's rival pro-EU alliance to form the next administration after eight years of right-wing populist rule.
Following the failed vote of confidence, the lower house of parliament – controlled by the pro-EU coalition – will now propose a prime minister to try to cobble together a working majority, and almost certainly that will be former EU chief Donald Tusk.
The conservatives had won the most seats in October's general election but found themselves without viable coalition partners, leading to Monday's vote in which only 190 lawmakers voted for the right-wing government of Mateusz Morawiecki, with 266 against.
While Tusk's Civic Coalition political group came second in the election, it secured a majority by joining up with two smaller pro-EU opposition parties, the Third Way and Left.
The trio had run on pledges that included mending strained ties with the European Union and carrying out liberal reforms.
"Today I would like to once again sincerely thank everyone who turned out to vote on October 15," the lower chamber's speaker Szymon Holownia of the Third Way said Monday.
"It is thanks to you that history is being made today," he added following the failed confidence vote.
Once nominated, Tusk on Tuesday is due to present his programme to MPs who will then hold a confidence vote.
The Tusk cabinet could be sworn in on Wednesday, allowing him to travel to Brussels for an EU summit on Thursday and Friday as the new prime minister.
Tusk has promised to unblock billions of euros in EU aid that have been frozen because of long-standing tensions between Brussels and the outgoing government.
Tusk has also said he will restore Poland's credibility in the EU and give it an important voice amid the ongoing war in neighbouring Ukraine.
President Andrzej Duda, an ally of the outgoing government, had entrusted the ruling Law and Justice (PiS) party with the first attempt to form the new government.
Speaking to reporters after the failed confidence vote, PiS leader Jaroslaw Kaczynski said "there had been some sort of societal misunderstanding".
Expectations for the new government are running high but the populists will remain very influential and have appointed allies to key posts during their eight years in power.
The next government will face daily battles with PiS which "will continue to fight", Jaroslaw Kuisz, a political analyst, told AFP.
"It will be like going through mud" and quick change will be difficult because PiS has left "a judicial minefield", he said.
Controversial judicial reforms and appointments, which the EU said undermined democratic values, were at the heart of tensions between PiS ministers and Brussels.
PiS still has allies in the presidency, the central bank and the supreme court, as well as in several important judicial and financial state institutions.
It also dominates state media organisations, which became government mouthpieces during its rule.
Analysts speak of a "spider's web" woven by PiS by putting allies in influential roles with mandates that will last long into the new government's tenure.
Duda is due to step down ahead of a presidential election in 2025 but he could use blocking tactics between now and then, vetoing legislation.
The head of state gave an insight into his intentions by nominating Morawiecki to try to form a government, giving PiS two more months in power.
Tusk on Friday said PiS has spent its last few weeks in power "wreaking havoc, destroying the Polish state."
Analyst Kuisz said the party has used the time "to reinforce itself institutionally and financially".
PiS has named two former ministers to head up important state financial institutions and selected new prosecutors.
The president has also approved 150 new judges nominated by a body that was criticised by the European Union as being too heavily influenced by PiS.
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