“He’s the lesser evil of the two,” was a commonly heard phrase at polling stations in Vienna, and Van der Bellen even used this pitch to undecided Austrians.

“I ask all those who don’t like me but perhaps like Hofer even less to vote for me,” he had pleaded ahead of Sunday’s runoff.

Greens celebrate as Austria’s far-right contender is defeated

In his first speech Monday as president-elect, Van der Bellen vowed to unite the divided nation, seeking to win the trust of the 2.2 million people who voted for Hofer. “There’s been a lot of talk about this country’s rifts. But I think you can also interpret the split as a sign that we are two sides of the same coin and each side is as important as the other. Together we make up Austria,” he said.

At 72, the grey-haired economics professor cut a somewhat dishevelled figure next to the polished Hofer, 45.

But first impressions can be misleading.

Van der Bellen’s decade-long career as leader of the Greens until 2008 has turned him into an agile and at times aggressive opponent in debates.

“I don’t want that Austria becomes the first country in western Europe led by a populist right-wing, pan-Germanic fraternity member,” he told voters.

He also vowed not to swear in FPOe chairman Heinz-Christian Strache as chancellor if the party, currently ahead in polls, wins the next general election scheduled for 2018.

The remark prompted Hofer to call him a “fascist green dictator”.

Increasingly sharp exchanges between the two men often degenerated into political mud-slinging, highlighting their glaring differences over issues like the migrant crisis.

Van der Bellen revealed he himself was a “child of refugees who has received a lot from Austria”.

Born in 1944 in Vienna, his father was a Russian aristocrat and his mother was Estonian. Both had fled Stalinism.

The arrival of the Red Army a year later forced the family to escape to the southern state of Tyrol, where Van der Bellen spent an “idyllic childhood”.

He studied economics at the University of Innsbruck and finished his PhD in 1970 before going on to become dean of economics at the University of Vienna two decades later.

Van der Bellen’s professorial manner has become a familiar feature, often riling Hofer.

“I’m talking about Europe: E-U-R-O-P-E. Never heard of it?” Van der Bellen taunted his opponent during a TV duel.

“My God, the schoolmasterliness, Herr Doctor Van der Bellen,” an agitated Hofer shot back.

Adversaries have also accused Van der Bellen of being a “turncoat” because he was a member of the Social Democrats before joining the Greens in the early 1990s and eventually becoming their president.

Under his leadership, the party went on to achieve record results, but he quit after the 2008 election when the Greens lost votes for the first time in almost 10 years.

As Austrian president, he dreams of a fence-free “United States of Europe” that defends the rights of minority groups.

An outspoken supporter of gay marriage, the divorced and recently remarried father-of-two garnered signatures from more than 4,000 public figures in the course of his presidential campaign.

This prompted a seemingly unimpressed Hofer to attack his rival for being too highbrow: “You have the glitterati, but I have the people,” he snapped.

In his private life, Van der Bellen admits to two weaknesses: Donald Duck comics and cigarettes.

“I once quit for four months... but why should I torture myself at my age!” he said of the latter.