AMSTERDAM — “People used to call us dirty communists,” says Filinta Karabulut, a 20-year-old member of the Socialist Party in Diemen, a working-class suburb of Amsterdam. “Now they come up to us and say we’re doing good work.”

This sea change in the Dutch mood experienced by Karabulut comes after 18 months of conservative government, with austerity policies and the euro-zone crisis driving widespread disaffection.

The Socialist Party’s supporters can taste victory amid the newfound respect. The most left-wing of the Netherlands’ mainstream parties, a group descended from 1970s Maoists, is poised to become the largest in parliament in elections next month.

A win by the Socialist Party and its leader, Emile Roemer, on Sept. 12 could mean a dramatic reversal for a country that has been one of the strongest advocates of austerity policies throughout the euro-zone crisis. If the party takes the Netherlands out of the German-led camp of countries pressing for stricter E.U. budgetary supervision in exchange for euro-zone rescue measures, it could shift the balance of power in Europe as a whole.

The Socialist Party has risen in part by opposing the government’s austerity policies. It takes a neo-Keynesian line on the euro-zone crisis — an approach that has gained credibility with voters as the Dutch economy has shrunk in the past three quarters.

“The economy needs stimulus,” Socialist member of parliament Harry van Bommel said at an election debate in Diemen this week, challenging government plans to raise the value-added tax, cut health-care subsidies and make it easier for employers to lay off workers.

“The reason businesses aren’t hiring isn’t because they can’t fire people — it’s because they see no consumer confidence,” he said.

In large part, however, the rise in support for the Socialist Party is attributable to its opposing euro-zone rescue measures as the Dutch grew increasingly fearful that they and their country’s triple-A credit rating have been put on the hook for debts incurred by southern European countries.

A traditionally euro-skeptic party, the Socialists voted against the rescue packages for Greece and more recently Spain, against the European budget pact and against the euro zone’s new European Stability Mechanism bailout fund, and it also opposes euro bonds and a European banking union. Although it was opposed to the euro in 1999, however, it is not calling for the country to leave the currency bloc.

The party’s preferred approach to the euro-zone crisis involves restructuring the debts of distressed sovereign nations and enlisting the European Central Bank to buy up their bonds. Roemer has recently moderated his tone on Europe in a bid to be seen as a legitimate candidate for the prime minister’s post.

But he still employs bursts of anti-Brussels rhetoric. Last week, he told the Dutch newspaper Financieele Dagblad that if the European Commission imposed fines on the Netherlands after a Socialist-led government failed to hit its required budget-deficit limit, he would refuse to pay.

“Should I pay some ridiculous fine if the deficit is above 3 percent [of GDP]?” Roemer said. “Over my dead body!” he added, breaking into English.

After widespread criticism, Roemer said he had not meant he would openly defy a commission mandate, and he jokingly promised to refrain from speaking in English.

The Socialist Party has profited from falling support for Labor, the traditional major party of the Netherlands’ center-left, which has backed the conservative government in approving the euro-zone rescue measures. Its tepid opposition has led many of its supporters to defect.

“It has become a bit of a colorless party,” said Margo Taal, a longtime Labor voter who attended the debate this week and said she is considering voting Socialist.

Meanwhile, the Socialists’ blanket opposition to every euro-zone rescue measure leaves observers unsure what Dutch E.U. policy will look like if they win the elections — and assuming they can form a government. Opinion polls suggest that if elections were held today, neither the Socialists nor their close rivals, the Liberals, could form a plausible coalition.

Van Bommel’s opponent, Liberal lawmaker Fred Teeven, said a Socialist win could lead to endless negotiations over a coalition.

“Roemer could spend four months after the election negotiating and then go back to the queen and say, ‘Sorry, we couldn’t do it,’ ” he said.

— Financial Times