BUENOS AIRES — A powerful federal judge in Argentina who handled a series of corruption cases against Vice President Cristina Fernández de Kirchner died early Tuesday morning, injecting uncertainty into the country’s most politically-fraught prosecution.

Judge Claudio Bonadio, 64, died nine months after undergoing surgery for a brain tumor.

Judges in Argentina play a critical role in investigating accusations, giving them the sort of power prosecutors wield in the United States. Judge Bonadio had worked on cases against Mrs. Kirchner and people close to her with unusual zeal, and it was uncertain whether many of his cases would be pursued at a time when her political power is on the rise.

Reactions to his death underscored how polarizing he became over decades on a bench that has long been infamous for its opacity and its tendency to meddle in national politics.

In the hours after his death, the phrase “divine justice” was trending on Twitter in Argentina as allies of Mrs. Kirchner, who was president from 2007 to 2015, criticized the judge. Her political opponents, meanwhile, flooded social media timelines with praise for the judge, who was on the bench for 26 years.