New Delhi, Jan. 15 -- Hungary's parliamentary election will take place on April 12, with the country's Prime Minister Viktor Orban expected to face his toughest challenge in 16 years.

President Tamas Sulyok announced the election date on Tuesday, urging people to vote. "One of the cornerstones of democracy is the right to vote freely," he wrote on social media.

The announcement comes as Orban and his nationalist-populist Fidesz party have been lagging behind the opposition Tisza party in most independent polls, the biggest disadvantage the prime minister has faced since taking office in 2010.

Tisza's leader, center-right lawyer Peter Magyar, 44, erupted onto Hungary's political stage less than two years ago and quickly built a politica...