Tens of thousands of protesters protested in Budapest on Saturday against the Prime Minister of Hungary, the ultra-conservative Viktor Orbán, called by a former member of his own circle, the lawyer Péter Magyar, who has announced his intention to challenge him with a new party.

Magyar, 43, burst onto the political scene a few weeks ago after the resignation – forced by Orbán – of the country’s president, Katalin Novák, and a former justice minister, Judit Varga, due to a controversial pardon. The scandal threatened to undermine Orbán ahead of the European elections on June 9, when Hungary will also hold local elections.

Péter Magyar, Varga’s ex-husband, defended both women and attacked Orbán and his “power factory,” and in March he made public a recording that sought to implicate a high-ranking minister in a corruption case. “I have not set out to defeat the entire power elite on my own; I am just the spark that can start that engine,” Magyar said at the march before Parliament.

Now, the new leader is gathering support to found a party with which to compete in the European elections. A poll gives him between 11 and 15% support. Opposition parties have gathered thousands of people against Orbán on other occasions, but what is notable this time is that the call came from a single person.