Voters went to the polls in Britain on Thursday in a dyspeptic mood, many of them frustrated with the Conservative government and skeptical that any replacement can unravel the tangle of problems hobbling the country.

Their skepticism is warranted, according to analysts. Even if the Labour Party wins a robust majority in Parliament, as polls suggest, it will confront a raft of challenges, from a torpid economy to a corroded National Health Service, without having many tools to fix them.

The Labour leader, Keir Starmer, would inherit a “legacy of ashes,” said Robert Ford, a professor of political science at the University of Manchester. And voters, who less than five years ago elected the Conservatives in a landslide, are not likely to give Mr. Starmer much slack to turn things around.

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In the 1980s, a French punk rock band coined a rallying cry against the country’s far right that retained its punch over decades. The chant, still shouted at protests by the left, is “La jeunesse emmerde le Front National,” which cannot be translated well without curse words, but essentially tells the far right to get lost.

That crude battle cry is emblematic of what had been conventional wisdom not only in France, but also elsewhere — that young people often tilt left in their politics. Now, that notion has been challenged as increasing numbers of young people have joined swaths of the French electorate to support the National Rally, a party once deemed too extreme to govern.

The results from Sunday’s parliamentary vote, the first of a two-part election, showed young people across the political spectrum coming out to cast ballots in much greater numbers than in previous years. A majority of them voted for the left. But one of the biggest jumps was in the estimated numbers of 18-to-24-year-olds who cast ballots for the National Rally, in an election that many say could reshape France.

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In the working-class neighborhood of Tehran surrounding Imam Hussein Square, the side streets and alleys are lined with secondhand stores and small repair shops for refurbishing all manner of household goods. But with little to do, most shopkeepers idle in front of their stores.

A 60-year-old man named Abbas and his son Asgar, 32, lounged in two of the secondhand, faux brocaded armchairs that they sell. Asked about their business, Abbas, who did not want his surname used for fear of drawing the government’s attention, looked incredulous.

“Just look down the street,” he said. “Business is awful. There are no customers, people are economically weak now, they don’t have money.”

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