Austria's anti-immigrant Freedom Party staked a claim to a role in the next government today after preliminary election results showed it had placed second behind the governing Social Democrats.

Chancellor Viktor Klima's Social Democrats made their poorest showing at the polls since World War II but still placed first with about 33 percent of the vote. The conservative People's Party, their governing partner for the past 13 years, fell to third place with 27 percent.

While the conservatives vowed to wait until the last votes were counted, the Freedom Party celebrated what leader Joerg Haider described as a "sensational breakthrough" when early returns showed they had bettered their previous showing by more than 5 percent to surge past the People's Party.

The dramatic gains by the Freedom Party, whose nationalistic appeals and xenophobic policies have stirred comparisons to the Nazis and other fascist movements, represented the biggest breakthrough by a far-right political party in Western Europe since World War II.

The results appeared to throw Austria's political landscape into turmoil, leaving its 8 million citizens uncertain about the shape of their next government. Klima has vowed never to form a coalition with Haider's group, which he has described as a repugnant political force driven by hateful ideology.

On the other hand, People's Party leader Wolfgang Schuessel insisted during the campaign that he would take his party into opposition if it finished in third place. So Klima must either persuade Schuessel to change his mind or hope that the conservatives will appoint a new leader more amenable to continuing their governing alliance.

Haider, 51, the telegenic son of a former Nazi official, attributed his party's success to the mounting frustrations of Austrian voters with the influx of illegal immigrants whom he blames for rising levels of crime, drug dealing and prostitution. He also attacked Austria's membership in the European Union as harmful to the nation's economic interests.

Fatigue with the governing parties--the Social Democrats and the People's Party--propelled Haider's party. But preventing Haider from entering government appeared to be the only motive the two parties had for remaining united for the past decade.

The Social Democrats and the People's Party have been battered by charges of cronyism and corruption, and they have constantly quarreled over economic and foreign policies. The conservatives want to sell off large-scale state interests and pushed hard to join NATO, but the Social Democrats favor maintaining a strong state sector and balked at sacrificing Austria's traditional neutrality to join the Western military alliance.

Earlier this year, many Austrians were appalled that neighboring Hungary found itself on the front lines of NATO's air offensive against Yugoslavia within two weeks of joining the alliance.

Nonetheless, the outgoing government's track record would seem enviable by the standards of other European nations. Austria enjoys some of Europe's highest living standards, and despite the anxiety about immigrants taking jobs, unemployment stands at just 4.3 percent and inflation is very low.

Haider says his blend of free-market and social welfare programs would liberate Austria from four decades of Socialist regulations and inject more entrepreneurial spirit into the economy. He advocates a flat tax of 23 percent and says his ideas about banning immigrants are no different than those of some American conservatives.

While focusing his pitch on Austria's antipathy to foreigners, Haider also tried to outflank the Social Democrats by proposing to restore an array of government benefits that Austria trimmed to meet the EU's budgetary requirements.

Haider was forced to resign as governor of Carinthia province in 1991 after his praise for the "sound employment policies" of the Third Reich was interpreted as an endorsement of slave labor. But he managed a comeback by regaining the office last year.

He also aroused criticism in 1996 by attending a convention of former members of Hitler's elite Waffen SS and lauding them as "decent people of character who stuck to their beliefs." Even though his father was a prominent member of the Nazi party, Haider insists that he abhors the Nazi history of genocide against the Jews and insists his anti-foreigner policies are rooted in a defense of current Austrian interests.

Many of Austria's 750,000 legal immigrants--less than 10 percent of the population--come from Turkey and the former Yugoslav republics. They toil mainly in menial jobs that many Austrians would disdain, and economists say their presence has become a key ingredient in the country's economic success.

Former chancellor Franz Vranitzky, a respected elder statesman who governed Austria for more than a decade before resigning largely out of disgust over Haider's ascendancy, warned that allowing the Freedom Party into power would damage the nation's image.

"There is no doubt that if Haider's party were to join the government, it would raise question marks about Austria in the eyes of the outside world," Vranitzky said. "And if we were to find ourselves isolated, it would mean the entire country would suffer."

CAPTION: Freedom Party leader Joerg Haider called the vote results a "sensational breakthrough."