A Far-Right Party Emerges as a Possible Kingmaker in Croatia

A far-right party emerged on Thursday as a potential kingmaker in Croatia after the governing conservatives finished first in a bitterly contested parliamentary election but fell short of winning enough seats to form a new government.

The outcome of Wednesday’s vote signaled a new era of messy political uncertainty in the Balkan nation, which has been dominated by one party, the Croatian Democratic Union, or HDZ, since 1991 when it declared independence from Yugoslavia.

The HDZ, led by the incumbent Prime Minister Andrej Plenkovic, won 61 seats in the 151-member legislature, according to the near-final official tally. That was more than all its rivals, including Rivers of Justice, a left-leaning coalition formed by President Zoran Milanovic, which won 42 seats to finish second. The far-right Homeland Movement finished third with 13 seats.

Speaking early Thursday in Zagreb, the Croatian capital, Mr. Plenkovic said his party had “convincingly won” but acknowledged that he would need help from rival groups to form a government and secure a third term as prime minister.

He later said in a post on Facebook that talks had already started with potential allies that he did not name. “Everything is going well,” he said, and predicted that a government would formed “soon,” putting a brave face on his party’s losses.

Tihomir Cipek, a political science professor at the University of Zagreb, said the result reflected a general trend in Europe, particularly among new members of the European Union, which Croatia joined in 2013. “The political center starts losing voters to parties to the far right and far left that are reaction to Europeanization,” he said.

Pressure from Brussels to adopt E.U. policies on gender and L.G.B.T.Q. rights, he said, “creates a type of protest which leads to support for far right politicians,” such as members of the nationalist Homeland Movement.

To stitch together a majority in Parliament, HDZ, badly tainted by a long series of corruption scandals, will most likely need support from the Homeland Movement and others. The Homeland Movement, favors staying in the European Union unlike similar groups elsewhere, and its support is unlikely to change Croatia’s stance on issues such as its support for Ukraine, analysts said.

“What I can say for sure, with full right and certainty, is that Homeland Movement is the third strongest party in Croatia,” the party’s leader, Ivan Penava, said in a postelection speech. He repeated promises made during the campaign to reject any coalition that included ideological opponents on the left or ethnic Serb legislators, saying that “In no way and under no conditions can they be our partners.”

But that left open the possibility of joining forces with HDZ, which began as a far-right party during the Yugoslav wars but has since evolved into a more mainstream conservative force. Homeland Movement opposes many of the governing party’s policies on Europe, particularly its decision to adopt the euro, the European Union’s common currency, but is closer to HDZ than to the left-tinged Rivers of Justice coalition, whose main component is President Milanovic’s Social Democratic Party.

The election campaign was dominated by a bitter personal rivalry between the prime minister, Mr. Plenkovic, and the president, Mr. Milanovic. The two men traded insults throughout the campaign: Mr. Milanovic denounced the prime minister as the “godfather of crime in Croatia” and Mr. Plenkovic accused his rival of being a Russian stooge and coward because of his opposition to helping Ukraine and his claim that NATO is responsible for Russia’s invasion.

When voters turned out on Wednesday, however, they rewarded neither man, gravitating in unusually large numbers to parties on the political flanks and giving the populist, far-right Homeland Movement a potential kingmaker role in forming a new government. The turnout of 62 percent was the highest in Croatia since 2000.

This election had been expected to be a sedate repeat of earlier races until President Milanovic announced an early vote and said that he would head the opposition campaign as its candidate for prime minister. Croatia’s top court declared his candidacy unconstitutional, ruling that he could not run to head the government while still serving as president. He ignored the ruling.

The president had not yet commented on the election results but Peda Grbin, the nominal leader of the Social Democrats, indicated the party would try to form its own coalition government to keep Mr. Plenkovic from staying in power.

“It is not over,” Mr. Grbin said. “Days, weeks and perhaps months of talks are ahead of us.”