Slovakia’s Election Could Echo in Ukraine. Here’s What to Expect.

An election in Slovakia on Saturday represents more than just a vote in a small Central European nation with less than six million people. It could also alter the contours of what has been a mostly united front in Europe against Russia’s war in Ukraine.

Slovakia, which shares its eastern border with Ukraine, has been one of the strongest backers of its neighbor since the start of Russia’s full-scale invasion, and was the first to send it air-defense missiles and fighter jets earlier this year.

But forces that oppose supporting Ukraine and the West are expected to make a strong showing in the election, and that could have far-reaching repercussions.

Here is what we know:

Who is expected to win?

For the past few years, Slovakia, which is part of the European Union, has been led by a pro-Western center-right government. That government collapsed in December and was replaced by a series of caretaker leaders.

Opinion polls show that the front-runner in the election Saturday is Direction — Social Democracy, or SMER, a populist left-wing party headed by Robert Fico. Mr. Fico is a former prime minister who has opposed sanctions against Russia and has railed against NATO, of which Slovakia has been a member since 2004.

The race has tightened significantly in the last few weeks, with SMER, though still ahead, losing ground to Progresivne Slovensko, a liberal party.

Because there are so many parties running — more than a dozen in all — no single party is likely to get anything like a majority. Slovakia has a proportional system, which helps smaller parties win seats and dilutes the ability of the bigger parties to form stable governments without help from rival parties.

The big question is not just who gets the most votes but who will agree to form a government with whom. Even if Mr. Fico’s SMER gets the most votes, it may not be able to form a government.

Mr. Fico, a pugnacious bruiser tainted by corruption scandals during his time as prime minister, is deeply unpopular with many voters outside the loyal base of his own party, which accounts for up to a quarter of the electorate. While nominally on the left, he also attracts some support on the far right. He resigned in 2018 following mass demonstrations over the murder of a journalist who was digging into evidence of government corruption.

In recent months, Mr. Fico has criticized the West and said that if elected, he would halt military support for Ukraine.

How did we get here?

From the beginning of the war, Slovakia has supported Ukraine. But pro-Russia disinformation has also proliferated in the country since the Russian invasion. Much of it is spread by pro-Russian groups in Slovakia on social media, and by news outlets known for recycling Russian propaganda, in what the country’s president, Zuzana Caputova, has described as a concerted campaign. Those messages have found fertile ground in a country where sympathies for Moscow run deep.

Experts say these polarizing narratives and messages capitalized on people’s frustration with skyrocketing inflation, high energy prices, dissatisfaction with the response of their leaders to the coronavirus pandemic, and bickering among governing politicians.

But they also build on the country’s history, said Katarina Klingova, a senior research fellow at Globsec, a policy institute in Bratislava, Slovakia’s capital. Many voters came of age when the country was controlled by the Soviet Union, and some have nostalgic memories of it, Ms. Klingova said.

A Globsec survey in March of public opinion across Eastern and Central Europe found that 51 percent of Slovaks believe that either Ukraine or the West is “primarily responsible” for the war. The figure is much lower in other Eastern European countries.

Why does the election matter?

A good performance by Mr. Fico and far-right parties that oppose supporting Ukraine would make the country officially more sympathetic to Russia. That would bolster a position adopted by Prime Minister Viktor Orban of Hungary, who has been outspoken in his opposition to helping Ukraine, but has so far been confined to the sidelines on the issue in Europe.

While Slovakia ranks 19th in terms of the resources it has sent to Ukraine, and a halt in its military support would not have major repercussions in the war, analysts fear that the success of parties who are opposed to helping Ukraine might aid Russia in creating fractures in the European front supporting the country.

Ms. Klingova also said that a victory for a populist party like SMER could push Slovakia closer to the model of “illiberal democracy” championed by Mr. Orban in Hungary, citing recent attacks on civil society organizations by several party leaders. Lubos Blaha, who is now the deputy leader of Mr. Fico’s SMER party, has also made inflammatory comments about L.G.B.T.Q. issues.

Other observers say that unlike Hungary, Slovakia has a very fragmented political landscape, making it more difficult for one group to push an illiberal agenda.

E.U. officials have also said that Slovakia’s election will be a test case of how susceptible countries in the European Union can be to Russian propaganda.