The trial has exposed deep fissures in Dutch society, which is known for its religious tolerance but has a more troubled recent past: More than three-quarters of Dutch Jews were deported and killed during the Nazi occupation in World War II.

The Netherlands was one of the six founding states of what became the European Union, but skepticism toward the bloc has been rising. In April, Dutch voters rejected a trade and cooperation agreement between the European Union and Ukraine, and after the British referendum on June 23 to leave the bloc, Mr. Wilders proposed that the Dutch hold a referendum on withdrawing as well.

Mr. Wilders, 53, is charged with offending members of a group based on their race, and hate speech and discrimination. If convicted he could be sentenced to up to two years in prison, though people found guilty of such offenses are more commonly fined or required to do community service.

A conviction could affect his career in Parliament, where he has been the leader of the Party for Freedom since 2006.