France, March 28 -- When far-right leaders from Europe attended an anti-Semitism conference in Jerusalem this week, it made headlines. Their parties have roots in Holocaust denial and Nazi collaboration- yet they were welcomed at an event aimed at fighting anti-Semitism.

The summit became a flashpoint. Several Jewish leaders, including Britain's Chief Rabbi, pulled out in protest. But the far-right presence wasn't a diplomatic misstep. It reflects a wider shift.

Among the delegates were Jordan Bardella, president of France's National Rally (RN)- formerly the National Front, founded by Holocaust denier Jean-Marie Le Pen - Marion Marechal Le Pen, niece of RN figurehead Marine Le Pen, and Bosnian Serb leader Milorad Dodik.

In response, Anti...