Former Secretary of State Mike Pompeo issued a rare rebuke of a Trump-backed candidate, breaking with his former boss to accuse Pennsylvania Senate candidate Dr. Mehmet Oz of dangerously close ties to the Turkish government.

Pompeo, who endorsed Oz’s chief rival Dave McCormick, cited reports that Oz voted in the 2018 Turkish elections instead of U.S. ones as evidence that the television personality, who holds dual citizenship, poses a security risk if elected.