WARSAW, Poland — Poland is holding an election Sunday that many view as its most important one since the 1989 vote that toppled communism. At stake are the health of the nation’s democracy, its legal stance on LGBTQ+ rights and abortion, and the foreign alliances of a country on NATO’s eastern flank that has been a crucial ally to Ukraine.

Political experts say the election will not be fully fair after eight years of governing by a conservative nationalist party that has eroded checks and balances to gain more control over state institutions, including the courts, public media and the electoral process itself.

Opponents of the ruling Law and Justice party fear it could be their last chance to preserve the constitutional system won at great cost through the struggle of many Poles.

The election “will decide the future of Poland as a country of liberal democracy, a system that has been a guarantor of Polish success for the last three decades,” the editor of the Rzeczpospolita newspaper, Boguslaw Chrabota, wrote in a Friday editorial.

Supporters of the ruling party, however, are afraid that if Law and Justice were voted out, the opposition would take the country in a more liberal direction, including laws legalizing abortion and civil unions for same-sex partners.

Recent polls show Law and Justice has more support than any other single party, but not enough to reach the majority in Parliament it would need to govern alone. It could be forced to seek support from a far-right party, Confederation, that is hostile to Ukraine.

The polls show that three opposition groups — Civic Coalition, Third Way and New Left — could together get a majority of seats in Parliament. The largest is the centrist Civic Coalition led by Donald Tusk, a former Polish prime minister and former European Union president.

Tusk has vowed to restore the rule of law and to rebuild ties with the EU that became severely strained under Law and Justice. The EU is withholding billions of euros in COVID-19 pandemic recovery funds from Warsaw, citing rule of law violations.

Small shifts for or against the smaller parties could significantly influence what coalitions will be possible after election day.

“So we have this situation of two sides who think that these are very high-stakes elections, two sides very determined and energetic. The emotions are very high, but the playing field is not even,” said Jacek Kucharczyk, the president of the Institute of Public Affairs, a Warsaw-based think tank.

The main reason for the imbalance is Law and Justice’s control of taxpayer- funded state media, which it uses to constantly bash opponents, Kucharczyk argued.

But other factors could play a role in the election’s outcome, including the party’s political control over the electoral administration and the chamber of the Supreme Court that will validate the election.

There is also a high level of state ownership in the Polish economy, and the ruling party has built up a system of patronage, handing out thousands of jobs and contracts to its loyalists.