(Bloomberg) — A rising star in Hungary’s opposition is set to lead the second mass protest in as many weeks in an effort to build grassroots support for a long-shot bid to challenge Prime Minister Viktor Orban’s rule.

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Peter Magyar burst onto the scene after the resignation of two key Orban allies, including Magyar’s ex-wife, former Justice Minister Judit Varga, in February.

The domestic fallout between the couple played out daily on social media and brought wider allegations of corruption into focus, helping Magyar to capture public attention in the eastern European country.

Read more: Orban Hit by Fresh Controversy After Ex-Insider Leaks Tape

Thousands are expected to join a protest outside the Hungarian parliament in central Budapest on Saturday organized by Magyar, a 43-year-old lawyer and former diplomat-turned-whistleblower.

Magyar, who’s yet to formally join a political party, plans to use the rally to detail his plans for challenging Orban’s party in elections for European Parliament and local municipalities set for June. A Republikon poll published on Friday by the news website Telex showed that a party led by Magyar would be instantly among the strongest opposition forces, though still well behind Orban’s Fidesz.

Corruption Case

Orban’s party has dominated Hungary since his return to power in 2010, and previous political upstarts have quickly flamed out or cannibalized support from existing opposition groups.

But Magyar’s release of a tape concerning a high-profile corruption case put the Orban’s cabinet temporarily on the defensive. In response, the formidable information machine controlled by the premier has unleashed a barrage of attacks against Magyar.

Under Orban, Hungary has plummeted to last place among European Union member states in Transparency International’s Corruption Perception Index. The EU continues to withhold two-thirds of the €30 billion ($32.5 billion) of Hungary’s funding it suspended in 2022 over corruption and rule of law concerns.

Orban’s officials have said Magyar, as a former executive of a state company, was a beneficiary of that system. He also held board seats in several other companies with state ownership until resigning to launch his political career.

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