BERLIN—Antiestablishment populism is on the rise in Europe, fueled not just by migration and economic and security fears, but by a deeper trend: Eroding confidence in governments’ ability to overcome those challenges. In Germany on Sunday, the far-right AfD and a new far-left populist party obtained almost half the votes cast in the eastern state of Thuringia, and together also took more than 40% in neighboring Saxony. In Thuringia, the AfD finished first, the first time a far-right movement has won a state election in postwar Germany.

In France, a legislative election that returned a hung parliament and gave the far-right National Rally almost a quarter of all seats—up sharply from the last election—has yet to yield a government two months later.

A litany of crises, from immigration to inflation and the war in Ukraine, has helped populists notch up electoral wins from Italy to the Netherlands and from Sweden to Finland in recent years. For some pollsters and analysts, however, crises are nothing new. What is new is voters’ crumbling confidence that elected governments can solve them.

“Crises are normally good for governments,” said Manfred Güllner, head of the Forsa polling group. “Voters rally around the flag. It happened after 9/11, after the financial crisis, even under Covid initially. Not today. Crises are piling up and support for the governments is at the bottom.”

In a Forsa survey of German voters published last week, 54% of respondents said they didn’t trust any party to solve the country’s problems. Only 16% said they trusted the government. Another survey of voters in France, Germany, Italy and Poland published by Sciences Po, a Paris-based university, earlier this year showed 60% of respondents had no trust in political institutions. The same proportion said democracy wasn’t working.

For Güllner, the rise of populist and upstart parties is the tip of an iceberg of disaffection, the submerged part is abstention. In Saxony and Thuringia, the share of non-voters has risen by 26% and 56% respectively since the first post-reunification election of 1990, he said.

Political indecision can be self-perpetuating. As voters lose trust in governments, they turn to populists and punish establishment parties, resulting in increasingly fractured parliaments . This, in turn, generates unwieldy and often indecisive coalitions that struggle to govern.

Even in France, where a two-round electoral system had long ensured stable majorities, political fragmentation is such that the past two parliamentary elections have returned hung parliaments. The latest in July still hasn’t produced a government.

“I used to think politicians had basic honesty. That’s over,” said Gérard Brauchli, 72, a retired ear, nose and throat doctor from central France. “They are not honest, not capable and they aren’t courageous.”

The loss of confidence is also palpable in Germany, whose economy has barely grown since 2019 and where years of underinvestment have fed a general feeling that nothing—from the police to the trains to the military , justice and education—is functioning any more.

After a Syrian asylum seeker killed three people in Germany on Aug. 23 in a terrorist attack claimed by Islamic State, authorities said the perpetrator should have been deported two years ago but it didn’t take place. Authorities tried to deport him in June last year but couldn’t find him. They didn’t try again, according to the regional government.

“The chancellor is losing control of his own country,” Friedrich Merz , leader of the conservative CDU opposition party, said after the attack. “This is the last straw.”

For Thomas Biebricher, a political scientist and writer on conservatism, Merz’s comment “raises the bar…It creates expectations that are unlikely to be met once you’re in government.”

Herfried Münkler, one of Germany’s leading political scientists, thinks the lack of trust in government is partly the product of strident populist rhetoric, whose alarmism creates a sense of urgency that no government can ever get ahead of.

At the same time, “crises are stacking up like layers in a cake faster than they can be solved,” he said, drawing an analogy with the 1920s in Europe. “Governments are overwhelmed…They are struggling to persuade people that while the problems are real, they are solvable.”

There are concrete reasons why governments may feel less effective today. In France, Italy and the U.K., high public debt is restricting governments’ policy choices. When newly appointed British Prime Minister Liz Truss unveiled plans for large unfunded tax cuts in 2022, worried investors caused a run on British government bonds, the pound fell to a record low against the dollar, and she resigned after six weeks in office .

Across Europe, a rapidly aging population has increased demand for medical treatment. Combined with a growing skills shortage in the health sector, this has led to longer waiting times for treatment, leading the World Health Organization to warn of an impending health crisis in the region.

Democratic states, ponderous by design with their thickets of laws and checks and balances, can be slow to react to crises. When the 2008 financial crisis broke out, threatening the banking system, the German government had to overrule decades-old parliamentary procedures to pass emergency legislation in days instead of months.

This built-in weakness has been a focus of populist attacks. In the early 2000s, the Polish populists and twin brothers Lech and Jaroslaw Kaczyński , then president and prime minister of Poland, denounced the strictures imposed by the rule of law as “legal impossibilism,” justifying their attempt to increase their executive powers.

In some cases, analysts say, the problems facing governments are so costly and complex to resolve that politicians end up pretending they don’t exist. An oft-quoted example is the absence of efforts by Berlin to reduce the share of natural gas that Germany imported from Russia after Moscow’s 2014 annexation of Crimea.

This left Berlin vulnerable to blackmail by the Kremlin, which began throttling gas deliveries to Germany after its full-scale invasion of Ukraine in 2022. Left without a choice, Germany did react in the end, turning to more expensive liquefied natural gas from the U.S. and elsewhere.

In a telling episode, Andreas Fulda, an expert on EU-China relations at Nottingham University in the U.K., spotted a senior Chancellery official at a reception in Berlin last June. Fulda approached him and asked why, in his view, the government was doing so little to reduce Germany’s economic reliance on exports to China, something Chancellor Olaf Scholz had pledged to pursue.

“His answer was: ‘Yeah right, Scholz can do everything’,” recalled Fulda. “By which he meant no, the chancellor can’t do anything about this, which was a very sobering admission.”

Berlin’s decision to welcome hundreds of thousands of asylum seekers stranded in Eastern Europe in August 2015 is another example. It backfired against the administration and marked the start of the AfD’s rise in popularity.

In his book Die Getriebenen—“the driven”—journalist and author Robin Alexander reconstructed the events of that summer as columns of migrants, mainly from the Middle East, embarked on a trek across the Balkans toward Germany. The narrative, later turned into a TV series, documented how Angela Merkel ’s government didn’t decide to open the borders, it just failed to close them, largely for fear of legal repercussions, effectively relinquishing control.

Today, political fragmentation is gumming up the work of governments, further undermining voter confidence. In Germany, Scholz’s three-way-government of Social Democrats, pro-market liberals and environmentalists—the first such coalition in postwar Germany—barely managed to agree on a budget this year amid constant internecine bickering.

“It could be that we are reaching the limits of political compromise,” said Münkler. “That’s not a good sign because this could push a majority of voters to call for a strong man or a strong woman. One who wouldn’t compromise but just decide.”

Write to Bertrand Benoit at bertrand.benoit@wsj.com