WARSAW — The nationalist Law and Justice (PiS) party that ruled Poland from 2015 to 2023 split on Friday in a political rupture that undermines the conservative camp’s attempts to topple pro-EU Prime Minister Donald Tusk in an election next year.

After the victory of conservative Karol Nawrocki in the presidential election of May 2025, PiS hoped it would build momentum toward a return to government in 2027. That prospect raised alarm in Brussels given PiS’s long track record of confrontation with the EU over issues such as the rule of law and LGBTQ+ rights.

But the party has been weakening in the polls since last fall and has been rocked by a battle over its political trajectory and succession between iron-fisted party leader Jarosław Kaczyński and former Prime Minister Mateusz Morawiecki.