When Republicans assume control of the House on Jan. 5, ending four years of a full Democratic majority in Congress, the president’s approach to policy and politics is poised to change on several fronts.

The White House is hiring more lawyers to handle oversight investigations from the new Congress, even as the president sets up a re-election headquarters in Chicago and considers ways to streamline operations inside the West Wing…

At the final cabinet meeting of the year, on Dec. 8, the president renewed his request that if any members intended to step down, they needed to signal their intentions. White House officials said they believed that Defense Secretary Robert M. Gates is the only cabinet member who definitely plans to leave next year, although one other departure is possible.