A Democrat takes over the F.D.I.C. after a partisan clash.

A Democratic bank regulator, Martin J. Gruenberg, has taken the helm at the Federal Deposit Insurance Corporation after a partisan fight prompted his Republican predecessor to resign.

Mr. Gruenberg became acting chairman of the F.D.I.C. on Saturday after Jelena McWilliams, who was appointed chairman by President Donald J. Trump, stepped down a day earlier.

In a statement laying out policy focuses for the year ahead, Mr. Gruenberg said regulators should carry out a review of bank mergers — the issue that prompted Ms. McWilliams’s exit. The F.D.I.C. is chiefly known for backing consumer deposits but has a hand in overseeing all of the nation’s banks.

“The F.D.I.C.’s core mission is to maintain stability and public confidence in the U.S. financial system,” Mr. Gruenberg wrote. To that end, he said its key priorities would be: reviewing the process of bank mergers, revising the Community Reinvestment Act, addressing the financial risks posed by climate change, providing guidance to banks around managing cryptocurrency assets and finalizing capital rules for banks that were introduced after the 2008 financial crisis.

In December, three Democratic members of the regulator’s board — Mr. Gruenberg, a longtime member; Rohit Chopra, the director of the Consumer Financial Protection Bureau; and Michael J. Hsu, the acting comptroller of the currency — voted over email to request public comment on the issue of bank mergers. Ms. McWilliams blocked those efforts, accusing other board members of trying a “hostile takeover” to wrest control from the head of an agency.