A high court ruling barring a crusading former prosecutor’s candidacy has turned Guatemala’s presidential election on its ear less than a month before the vote, and raised concerns about what will happen to years of efforts to fight endemic corruption.

The rejection of Thelma Aldana’s appeal means at least two of the top three candidates according to polls will not appear on the June 16 ballot, and analysts said Thursday the Aldana decision in particular appeared to spring from fears over her zealous prosecutions of corruption in politics and business.

“I think that the deeply entrenched, established powers that be in Guatemala are absolutely terrified of a candidate like Thelma,” said Christine Wade, a political scientist at Washington College in Maryland. “She has a proven record as attorney general of jailing former presidents and vice presidents. … And it’s really difficult to see this constitutional court decision as anything other than politically motivated.”

Aldana’s candidacy was denied on the grounds that she lacked a document accrediting that she didn’t have any outstanding accounts after having been responsible for public funds from her time in office.