BERLIN — Less than a week after the mass killings in Norway, evidence of a shift in the debate over Islam and the radical right in Europe already appeared to be taking hold on a traumatized Continent.

As the police in Norway and abroad continued to search for potential accomplices, expressions of outrage over the deaths crossed the political spectrum. Members of far-right parties in Sweden and Italy were condemned from within their own ranks for blaming multiculturalism for the attack. A member of France’s far-right National Front was suspended for praising the attacker.

Lurking in the background is the calculation on all sides that such tragedies can drive shifts in public opinion. Nonviolent political parties can hardly be blamed for the violent actions of a terrorist or a homicidal person. But politicians have begun to question inflammatory speech in the debate over immigrants, which has helped fuel the rise of right-leaning politicians across Europe in recent years.

The head of the Social Democratic Party in Germany, Sigmar Gabriel, told the German news service dpa on Wednesday that a trend toward xenophobia and nationalism in the region had fostered the attacks in Norway. In a society where anti-Islamic sentiment and isolation were tolerated “naturally on the margins of society, there will be crazy people who feel legitimized in taking harder measures,” he said.