Haley Stevens' endorsement of Republican Mike Rogers prompted aides to leave her operation, turning the Michigan Democrat's break with her party into an immediate campaign crisis.
Mike Rogers was the rival named in the endorsement, and the backlash quickly spread beyond staff departures to angry reactions from Democratic allies highlighted in election coverage.
The rupture lands as voters head to the polls in a midterm cycle Fox described as high stakes, with prediction markets topping $1.2 billion and control of Congress still in play.