For the first time, Austria's next president will likely be someone who is not officially backed by either of the two parties that have dominated politics since the end of World War II. That reflects massive voter unhappiness — and spells possible political turmoil ahead.

The steadily eroding popularity ratings of the governing coalition — made up of the center-left Social Democrats and the centrist People's Party — are reflected in the dismal chances of their candidates in Sunday's presidential election, compared with the right-wing Freedom party hopeful and two others running as independents.

Social Democratic candidate Rudolf Hundstorfer has 15 percent support and Andreas Khol, his People's Party counterpart, 11 percent. That compares with support of between 22 and 24 percent for Freedom Party candidate Norbert Hofer, and independents Alexander Van der Bellen and Irmgard Griss, according to an OGM survey published six days before the vote.

Strongly criticized over its handling of the migrant crisis, the government coalition has swung 180 degrees this year as it tries to claw back support lost to the Freedom Party. It has turned from open borders to one of the EU's most restrictive asylum regimes.

But the two mainstream parties have been foundering even ahead of the presidential election and long before the migrant crisis.

The Social Democrat-People's Party coalition is a marriage of necessity. That has meant decades of bickering, most recently over tax, education and pension reform — leading to deepening voter disillusionment.

A win by any of the three front-runners in the presidential election spells trouble for the two mainstream parties. At best it will result in more pressure from the top from a president not beholden to them. At worst, Freedom Party candidate Hofer has threatened to dismiss the government coalition and call a new national election.

An Austrian president has the powers to dismiss a government. But none has since the office was newly defined after World War II. Instead the role has been traditionally ceremonial, with presidents rarely going beyond gentle criticism of the government.

Fueled by the migrant crisis, Hofer's party now is backed by 32 percent of voters, compared with just over 20 percent for coalition parties. A new national election would almost certainly lead to a Freedom Party victory and threaten to swing Austria toward the Euroskeptic, anti-foreigner orbit now occupied by Hungary and other East European EU members.

With Austria among the world's most prosperous and stable nations, voter dissatisfaction appears disproportionate. But political scientist Anton Pelinka points to the popularity of U.S. Republican Party presidential candidate Donald Trump in arguing such anti-establishment sentiment is not unusual.

Austria's two mainstream parties "are identified with the status quo," he says. "While this (status quo) is not exactly a catastrophe for Austrians, it has become the object of an occasionally not very rational, often enraged rejection, a la Trump."

No candidate is likely to get the absolute majority Sunday, meaning a likely second voting round on May 22. Judging by the polls, that will match up Hofer against either Griss or Van der Bellen.

Whoever opposes Hofer is expected to be able to line up a sizable number of votes from Austrians who backed the socialists or centrists in round one but are opposed to the Freedom Party.

Still, political uncertainty may lie ahead, even if Hofer is defeated.

Van der Bellen, a member of the Greens party who is running as an independent, has vowed not to swear in any Freedom Party politician as Austria's chancellor if he wins Sunday's vote.

The next national elections must be held within two years. The president has a six-year mandate. That means possible confrontation between the Freedom Party and Van der Bellen, should he triumph.

One thing is for sure, says Pelinka. The era of prolonged dominance by one or the other party is ending.

"Austria was overly stable in the political sense for too long," he says.

"Now comes the phase of a low political stability."