President-elect Trump nominated Rep. Elise Stefanik (R-N.Y.) to serve as U.S. ambassador to the United Nations on Monday, further elevating her seismic rise in the Republican Party. It is a major

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.

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