Sen. John Fetterman's chief of staff resigned Wednesday, a source familiar with the move told Axios. Why it matters: The Pennsylvania Democrat has had a serious staff retention problem as he's faced scrutiny over his health struggles and changing political brand. Driving the news: Cabelle St. John has served on Fetterman's team since he first came to Washington about three-and-a-half years ago. She became his chief of staff in 2025. Her official last day will be in the coming weeks. Fetterman,