Serbia’s Election Shows New Vulnerability for Nationalist Populists In much of Europe, the advance of the right has been seen as unstoppable. But in the east, nationalists are being cast aside in places where they long governed.

When voters in Hungary rejected their seemingly invincible populist leader Viktor Orban in April, Andrej Borovac, a young designer in neighboring Serbia, was ecstatic, but he was downbeat about his own country’s populist strongman suffering the same fate.

“That can never happen here,” he recalled thinking. Aleksandar Vucic, Serbia’s dominant political figure since 2012, looked immovable, given his grip — established over more than a decade in power — on security forces, nearly all major media outlets, the electoral commission and many other institutions. Or so he thought. On Sunday night, Mr. Borovac, 38, and two friends joined tens of thousands of people gathered near Parliament in Belgrade, the Serbian capital, to celebrate Mr. Vucic’s defeat in a pivotal election for a new legislature.

“The Hungarian Spring has come to Serbia in the fall,” Mr. Borovac said late Sunday night, surrounded by revelers waving Serbian flags and setting off red flares. Nearby, a group of young Serbs danced for joy.

At a time of rising liberal fears of surging support for right-wing nationalists, the formerly Communist East, an early pioneer of populist politics after the collapse of Soviet hegemony in 1989, is showing that tides can turn.

Elections this year in Hungary and Serbia, and in Poland in 2023, have given new life to mostly forgotten liberal hopes voiced in “The Power of the Powerless,” a 1978 book by Vaclav Havel, the Czech dissident who would later become president and a global icon for believers in liberal democracy.

Anger at rampant corruption helped glue together disparate and sometimes contradictory political forces, allowing them to campaign on an issue that resonated with a wider population upset by the conspicuous wealth of people connected to the governing party.

In Germany, France and Italy and elsewhere in Western Europe, the anti-establishment nationalist camp has taken on the appearance of an invincible juggernaut, and it may yet show strongly in a raft of elections next year. But for the moment, in Eastern Europe and beyond, it is newly showing signs of strain.

On the same day as Serbia’s election, voters in Brazil narrowly rejected an all but preordained victory for the hard right and handed a win to the leftist president, Luiz Inácio Lula da Silva.

The Serbian election will also add to the discomfit of President Trump’s MAGA movement, which for now lags in many polls ahead of what is expected to be a difficult election next week. It had looked to the Serbian leader as a kindred spirit committed to defending national sovereignty and resisting European liberals. Mr. Trump’s family eyed it for business deals.

A few weeks before the election, the Conservative Political Action Conference, or CPAC, a MAGA-aligned American organization, announced that it would hold its first gathering in the Balkan region, to be held in Belgrade in November and “headlined by President Aleksandar Vucic.”CPAC had previously focused its European activities on Hungary, where it held a big annual gathering, now in doubt following Mr. Orban’s defeat and the end of state funding by the new government to foundations that helped bankroll various ventures by “anti-woke” warriors from abroad.

Even in Eastern Europe, the momentum has not been all one-way, and it often zigzags. Parliamentary elections in Slovenia this year and the Czech Republic last year as well as a presidential vote in Poland all saw nationalist forces prevail, albeit by tiny margins.

Also, the forces that have proved ascendant against the nationalist right are themselves a mixed bag that are far from being liberal globalists. Mr. Orban was defeated by a new party led by Peter Magyar, a conservative former Orban loyalist, and Mr. Vucic by a slate of student-selected candidates, nearly all newcomers to politics.

Thorsten Benner, director of the Global Public Policy Institute in Berlin, said the lesson from both Hungary and Serbia was that “at some point, anti-incumbency bias or rage hits these authoritarians,” though the alternative “won’t be picture-perfect liberals.”

“The real positive lesson,” he added “is that these authoritarians can actually lose elections and concede defeat.”The political party that underpinned Mr. Vucic’s long ascendancy is called the Serbian Progressive Party, hardly a right-wing outfit. It has railed against privatization and vowed to keep big chunks of the economy, which has grown robustly, under state control.

After a record turnout of nearly 70 percent, his party won 39 percent of the vote compared with 52 percent for its main opponent, a new political grouping that emerged from nearly two years of student-led protest called Student List-Students Win.

The Student List has itself embraced nationalist themes. Many of the people rejoicing Sunday night on the street flashed the three-finger Serbian salute, a patriotic gesture used by marauding ethnic Serb troops during the Balkan wars of the 1990s.

Miljana Pejic, 33, a youth trainer who joined Sunday night’s street celebrations, said the salute in its current use was not a throwback to dark nationalist passions but a “reclaiming and reframing of Serb symbols” that had been hijacked.

“We love our country so perhaps we are nationalist,” she said, “But everything the students advocate — the rule of law, anti-corruption, independent institutions — is in line with the values of the European Union,” she said.

Serbia applied to join the European bloc in 2009, but its application largely stalled under Mr. Vucic, whose brand of nationalism and illiberal politics closely resembled that of his ally Mr. Orban in Hungary.

In the end, both men nonetheless conceded defeat when it became obvious that the groundswell of discontent from voters had overwhelmed their best, years-old attempts to tilt the political playing field their way, not least by manipulating the media.

In an early concession speech Sunday evening, Mr. Vucic lamented that “they toppled us,” blaming his defeat on shadowy foreign forces. The election result, he said, “was the verification of a revolution carried out with direct support from various European countries and the American deep state — the one opposed to President Trump.”But his biggest problem, as was Mr. Orban’s, was that the election largely became a referendum on himself: he had stopped being popular and, accused of ties to gangsters, become instead a hate figure for large segments of the population, no matter what their political orientations.

Dimitar Bechev, a senior fellow at Carnegie Europe and an expert on the Balkans, said he was surprised by the opposition’s wide margin of victory but added: “You overstay your welcome after many years.”

In both Hungary and Serbia, he said, “when you have a strongman figure, you have a coalition from liberals to people on the far right fed up.”Bozo Prelevic, an opposition-aligned lawyer, on Monday compared Mr. Vucic to a malignant tumor. “Serbia has freed itself after a long and serious illness, a cancer that was destroying both society and the state, setting citizens against one another and invoking war,” he told N1, an opposition-friendly television channel.

It is unclear what the Student List’s victorious candidates want to do in terms of policy once they take their seats in a new Parliament, which must convene within 30 days of the announcement of the final results. Their campaign revolved around a single issue: getting rid of Mr. Vucic and uprooting what they called his corrupt “mafia.”The slate of candidates selected by student activists includes no students and comprises academics, musicians, activists, actors, athletes and others from a wide range of backgrounds. Most have no experience in politics or government.

The first candidate on the list was Ilija Srdanovic, a cardiologist from the city of Novi Sad, but he is not the head of a hierarchical party with power to set policy and tell fellow Student List members of Parliament what to do.

In his first public remarks after the election, Mr. Srdanovic chided those who had questioned whether such an amorphous political movement could defeat Mr. Vucic.

“We believed not just in victory, but in a victory so clear that it could not be concealed,” he told RT Balkan, a Russian state-funded news outlet aimed at Serbia.

Alisa Dogramadzieva contributed reporting from Belgrade, and Steven Erlanger from Berlin.

An earlier version of this article misstated the name of the American political organization that is planning an event in the Balkan region in November. It is the Conservative Political Action Conference, not the Consultative Political Action Conference.

We acknowledge mistakes in our reporting with corrections. If you spot an error, please let us know at corrections@nytimes.com. Learn more. Andrew Higgins is the East and Central Europe bureau chief for The Times based in Warsaw.