Georgia Secretary of State Brad Raffensperger, who won a surprise victory against a Trump-backed opponent in Tuesday’s Republican primary, is slated to be one of Willis’ lead witnesses when he appears before the grand jury next Wednesday, sources confirmed to Yahoo News.

“Based on her pugnacity, it looks like it’s full steam ahead,” said one lawyer representing a client who has been contacted by Willis’ team of investigators and prosecutors. “She’s much more aggressive and determined than I expected.”

Willis’ investigation appears to now represent the biggest single legal threat to Trump, given there have been no clear signs that prosecutors at the U.S. Department of Justice or the New York District Attorney’s office are actively preparing to bring criminal charges against the former president. She has assembled a team of about ten prosecutors and agents for the Trump probe. Earlier this month, a group of them flew to Washington to meet with investigators from the Jan. 6 committee, who shared details from confidential witness testimony and other material relevant to Trump’s efforts to flip Georgia’s 16 electoral votes, said a source familiar with the probe.