Budapest: Hungarians were casting ballots Sunday in what is widely seen as Europe’s most consequential election this year, a vote that could unseat populist Prime Minister Viktor Orbán, after 16 years in power.

It’s a key moment for Orbán, the European Union’s longest-serving leader.

Polls opened at 6 a.m. local time and were scheduled to close at 7 p.m. Orbán and his top challenger, Péter Magyar, were expected to cast their votes later in the morning.

The election was being closely watched in countries around Europe and beyond.