BUDAPEST, Hungary — With Hungary's parliamentary elections still five months away, the country is already immersed in an intense political campaign between Prime Minister Viktor Orbán and his challenger, Péter Magyar, that promises to be the biggest challenge of the nationalist leader's career.

Elected for a first term in 1998 and then for four more terms beginning in 2010, Orbán has stood at Hungary's helm for 20 years. Beloved by his supporters but accused by his critics of corruption and authoritarian tactics, he has overseen a political system in which his far-right Fidesz party has exercised nearly unchecked power.

But now, support for Europe's longest-serving leader is declining amid poor economic performance and chronic inflation, and a challenger who has shifted the political tid

See Full Page