The SEC is normally governed by five commissioners, including three from the president’s party and two from the other. President Barack Obama nominated two candidates to fill the existing vacancies more than a year ago, but the gridlocked Senate hasn’t confirmed them. Republican Commissioner Michael Piwowar is likely to lead the agency as acting chairman after Ms. White exits, although Mr. Trump could nominate someone else as Ms. White’s permanent successor.
via SEC Chairman White to Leave Agency, Opening Door to Conservative Shift – WSJ.