- Norbert Hofer could become first far-right leader in Western Europe since World War II
- The election is a rerun after May's original vote was annulled over ballot irregularities
If Hofer wins, he would become first far-right president in Western Europe since the end of World War II.
Not only are the two from opposite sides of the political spectrum, but it's the second time this presidential election is being run.
It was originally held in May, with former Green Party leader Van der Bellen defeating Hofer by little more than 30,000 votes in a tightly fought contest decided by mail-in ballots.
But the results were annulled over concerns about how some ballots were handled
. So the two candidates, with widely different outlooks, are meeting again in a rerun.
While the Austrian president's role is largely ceremonial, the vote is being closely watched from elsewhere as a yardstick of wider anti-establishment sentiment.
Hofer's party has risen on a populist groundswell sweeping the continent caused by the European Union's failure to make progress in the ongoing economic and migrant crises.