New year, new administration and, soon, a new chairman for the Commodity Futures Trading Commission.

Timothy G. Massad, the chairman, said he would step down at the start of Donald J. Trump’s presidency. His resignation comes after Mary Jo White, the chairwoman of the Securities and Exchange Commission, said in November that she planned to leave at the end of the Obama administration.

Jay Clayton, a Wall Street lawyer who has worked on prominent public offerings, is a leading candidate for chairman of the S.E.C., according to Reuters, which cited two sources familiar with the matter.

There are also other unfilled seats at both agencies, which means the Trump administration will play a significant role in shaping the oversight of financial markets.

The president-elect has not yet indicated his choice for the top job at the C.F.T.C., and J. Christopher Giancarlo (the lone Republican on that commission’s panel) is expected to lead the agency in the interim.