At the same time, Mr. Marcouch said, Dutch politicians were promoting economic integration — language training, job training. “They didn’t understand the importance of religious identity among the immigrants,” he said. They dismissed it as backward even as they failed to understand the anger a growing immigrant population was creating. “The fear,” he said, “is on both sides.”

Some, like Rob Riemen, director of the Nexus Institute, a research organization, think that Mr. Wilders represents a new fascism, using Islam as the scapegoat for every ill. “Wilders was a key source of inspiration for Breivik,” Mr. Riemen said. “But the Dutch don’t want to acknowledge that we see fascism in the face of Wilders. To call him a populist is to disguise what is really going on.”

Social democracy has lost its way and become too tied to materialism and the market, Mr. Riemen said. “And history teaches us that fascism pops up when social democracy loses its compass.”

But others argue that analogies to fascism overstate the weakness of Dutch society and the appeal of the far right. Paul Nieuwenburg of Leiden University says that many issues are jumbled together in the growing revulsion against immigration: fear of “Islam,” as if it were monolithic; of terrorism; of globalization; of joblessness; of the growing influence of European Union bureaucrats in Brussels; of austerity; of the perils to the euro and the Dutch budget of Greek, Portuguese, Irish, Spanish and now Italian debt; of juvenile criminality, especially among youth from Morocco and the Antilles.

“There is a growing protest vote,” Mr. Nieuwenburg said. “People feel let down by the traditional parties.” And the traditional parties, reacting to the rise of Wilders, have all fled from the language of multiculturalism. “The taboos are gone, and now you’re suspect if you say anything positive about multiculturalism,” said Henk Overbeek, a political scientist at VU University.

The Labor Party thought it would win the 2010 elections by fielding Job Cohen, a former mayor of Amsterdam who was a champion of multiculturalism. Mr. Cohen now takes a less accommodating tone, speaking of the problems of immigration, dislocation and juvenile crime to the native population. “They feel they have moved without moving,” he said. “They live in the same house as 30 years ago, but the environment has changed.”

Mr. Cohen calls the government’s reliance on Mr. Wilders “the worst possible solution, because it gives him a lot of influence without responsibility.”