Sunday's showdown pits 45-year-old Norbert Hofer of the anti-immigrant Freedom Party (FPOe) against the Green-backed economics professor Alexander van der Bellen, 72.
In previous encounters, the pair had traded increasingly aggressive barbs, exposing their glaring differences over the migrant crisis and the European Union.
The mud-slinging reached a crescendo last weekend when they tore each other down for 45 minutes on private Austrian channel ATV without a presenter to moderate the debate.
"My God, the schoolmasterliness, Herr Doctor Van der Bellen," his agitated rival shot back.
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Commentators afterwards "described the show as an "embarrassing" fiasco.
In contrast, yesterday's 100-minute-long debate on the public broadcaster ORF was a mostly subdued affair, primarily summarising the candidates' main campaign points.
"If you put two gladiators in an arena, it can happen that the two argue in a heated manner," said Hofer as he tried to downplay last Sunday's fiasco.
The far-right candidate went on to reiterate his intention to be "a much more active" president.
Hofer has previously threatened to seize upon never-before-used presidential powers to fire the government if it failed to get tougher on migrants or boost the faltering economy.
Traditionally, the role has been held by a candidate from one of Austria's two main centrist parties since 1945.
But their crushing first-round defeat has now pushed Austria into unfamiliar territory.
However, Hofer -- who is also a lower house leader in the Austrian parliament -- stressed that his "personal views and values" would not prevent him from being a "non-partisan president".