Washington ? President-elect Barack Obama officially resigned from the Senate Sunday, removing himself from any official role in the lame-duck session of Congress that will convene this week. He also laid more groundwork for the start of his administration by deciding on additional members of his staff, including a White House counsel, and preparing to meet with another onetime political rival.

Obama is scheduled to meet today with Sen. John McCain, R-Ariz., whom he defeated in the Nov. 4 presidential election, at his transition offices in downtown Chicago. The meeting comes days after the president-elect sat down separately with Sen. Hillary Rodham Clinton, D-N.Y., and New Mexico Gov. Bill Richardson, both of whom opposed him in the Democratic primary.

Washington lawyer Gregory Craig will be White House counsel, according to an individual involved in the transition, and Obama’s Senate chief of staff Peter Rouse, 62, was officially announced as a senior White House adviser

Thus far, Obama’s selections have been mostly a mix of Washington veterans – many with ties to the Clinton administration – and trusted campaign aides. Late last week, the president-elect named close friend and adviser Valerie Jarrett as a senior White House aide. Campaign strategist David Axelrod will also hold a senior advisory role.