Hatch Act rules dictate that as a government employee, Stefanik could not fundraise and would be permitted to give political speeches only in a personal capacity, according to ethics expert Richard Painter, who served as an official in President George W. Bush’s administration.

Stefanik serves as House Republican Conference Chair and has long been one of Trump’s most loyal allies in the House.

Ms. Stefanik, who chairs the House Republican Conference, undertook a dramatic transformation that brought her to the center of Donald J. Trump’s orbit.