“The party has played on the country’s sense of wounded pride to make Roma and Jews the scapegoats for everything that has gone wrong,” he said, “even if many Jobbik voters have never even seen a Jew.”

Image Viktor Orban, the Fidesz party leader and former prime minister, celebrating with supporters in Budapest on Sunday. Credit... Balint Porneczi/Agence France-Presse — Getty Images

Analysts said Jobbik’s pledges of restoring law and order also resonated with voters frustrated by what they see as endemic corruption and duplicity among the ruling Socialist Party. Last year, Ferenc Gyurcsany, a Socialist, resigned as prime minister, saying he considered himself a hindrance. In the autumn of 2006, Mr. Gyurcsany admitted in a secretly taped speech leaked to the media, that his party had “lied” about the state of the economy before elections that spring.

Hungary is among the countries in Eastern Europe hit hardest by the financial crisis. In late 2008 it was forced to approach the International Monetary Fund for $25 billion in emergency financing. Unemployment has soared to 11.2 percent and the economy contracted in 2009 by 6.3 percent. The Socialist government has raised taxes and slashed spending, helping to reduce Hungary’s budget deficit to 4 percent of gross domestic product in 2009, from 9.3 percent in 2006.

But while the measures have stabilized Hungary’s finances, they have alienated many voters.

Some economists fear that the growing influence of Jobbik, which wants to eliminate tax rules favoring foreign companies, could undermine the country’s economic recovery by alienating already jittery investors, spooking credit agencies and making it harder for the country’s next prime minister to shepherd the economy.

Gergely Boszormenyi Nagy, chief analyst at the Perspective Institute, a research center in Budapest, said a Fidesz government would have a strong enough majority in Parliament to follow through on its economic agenda, including implementing the economic measures prescribed by the I.M.F. Moreover, he stressed that Fidesz had distanced itself from Jobbik.

Nevertheless, he argued that Jobbik’s ascent could wreak havoc with Hungary’s country brand.

“The success of Jobbik could make it hard to communicate Hungary as an open, business-friendly environment,” he said.

Peter Rona, an economist, said that even without Jobbik’s corroding influence on investor confidence, Hungary remained mired by the high levels of household indebtedness that had helped spur the country’s economic crisis in the first place. “People are ignoring that the credit mess hasn’t changed,” he said.