The two main parties, the Social Democrats (SPÖ) and the centre-right People's Party (ÖVP), have between them run Austria since the end of World War II, but support has been sliding in recent years.
At the last general election, in 2013, they only just scratched together a majority, and polls suggest they will struggle to do so again at the next scheduled ballot in 2018.
In a latest blow, their presidential candidates failed even to make it into the runoff on May 22 in what Austrian media called a political "tsunami".
The crushing defeat means that for the first time since 1945, the president will not come from one of the two main camps.
Instead, the head of state will either be Norbert Hofer of the far-right Freedom Party (FPÖ) or Green-backed contender Alexander van der Bellen.
The far-right's electoral success is partially based on its promise to abolish Austria's so-called "Proporz" power-sharing system, which allows ruling parties to hand out public positions in proportion to their political strength.
Instead, Hofer wants to model the country on Switzerland and create a "direct democracy", putting political decisions to a referendum.
No more pariah?
The FPÖ, under its leader Heinz-Christian Strache, now consistently scores more than 30 percent in opinion polls.
As a result, the party has repeatedly called for snap elections, holding high hopes it will be able to join the government like it did back in 1999 under Strache's charismatic predecessor, the late, SS-admiring Jörg Haider.
Back then, the party scooped second place and entered a much-maligned coalition with the ÖVP, prompting international sanctions and turning Austria into an EU pariah.
This time, however, observers note there could be less of a backlash in light of surging support for populist parties elsewhere in Europe.
Fresh wind for eurosceptics
A far-right victory could also give further impetus to eurosceptic parties which have surged in popularity across the continent.
In light of the ongoing Brexit debate, Hofer has indicated he was "not in favour of leaving the Union" -- unless Turkey becomes a member of the bloc.
Back in 1994, he voted against Austria joining the EU.
Meanwhile Hungary's right-wing Prime Minister Viktor Orban, known for his angry tirades against Brussels, would find a new ally in Hofer.
The Austrian government's criticism of Budapest's hardline stance on migrants "was a grave diplomatic error which I want to correct as president," Hofer told French weekly magazine Valeurs Actuelles in a recent interview.
"Declaring that Hungary is close to fascism just because it's the only country to apply the Schengen rules... is absurd."
The migration crisis, which has been rattling Europe since last year, has boosted the supporter base of new formations like the Germany's AfD, now the country's third-strongest party, or the neo-nazi Our Slovakia party.
It has also given fresh impetus to long-established far-right parties like the FPÖ and France's Front National.
Sunday's vote is likely to be closely followed by FN leader Marine Le Pen who has her sights firmly set on winning next year's presidential election.
"Magnificent result," she jubilantly declared after Hofer's surprising first-round victory.
Last year, the FPÖ and FN formed a bloc with other far-right EU parties to fight what they called the "Islamisation" of Europe.
Strache recently accused German Chancellor Angela Merkel and Italian Prime Minister Matteo Renzi of being "people-smugglers" over their handling of the refugee crisis.