The far right surged to almost a third of the vote in Austria's parliamentary election on Sunday, complicating prospects for the biggest mainstream party, the Social Democrats, to forge a viable coalition government.
Preliminary official results showed Heinz-Christian Strache's far-right Freedom Party scored 18%, compared with 11% two years ago, while Joerg Haider's right-wing populist Alliance for Austria's Future was on 11%, almost tripling its vote haul in 2006.
The two parties split acrimoniously in 2005, and a major question now is whether the two might cooperate to bolster the right's case for a share of power.
The centre-left Social Democrats at 30% and the conservative People's Party at 26%, down from 35% and 34% respectively in 2006.
It was the worst showing for both since World War Two.
But by retaining their status as the largest single party, the Social Democrats under Werner Faymann are expected to be asked by Austria's president to form the next government.
The right's record showing heralded political instability, since the two main centrist parties will be hard put to re-establish a broad coalition even if they resolve the feuds that killed off their last alliance.
Final results will not be released until 6 October after absentee and postal ballots, making up about 10% of the votes, are counted.