President-elect Barack Obama began moving Wednesday to build his administration and make good on his ambitious promises to point the United States in a different direction, as his commanding victory reordered the American political landscape and transfixed much of the nation and the world.

A day after becoming the first African-American to capture the presidency, Mr. Obama announced a transition team and prepared to name an ally as his White House chief of staff in his first steps toward assuming power. President Bush vowed to work closely with Mr. Obama to ensure a smooth transition in the first handover since the attacks of Sept. 11, 2001.

Representative Rahm Emanuel of Illinois, the fourth-ranking House Democrat and a close friend of Mr. Obama’s from Chicago, has been offered the job of chief of staff, and although he was said to be concerned about the effects on his family and giving up his influential role on Capitol Hill, many Democrats said they expected him to accept it. Mr. Obama named John D. Podesta, the former Clinton White House chief of staff, to lead his transition team along with Valerie Jarrett, a longtime adviser, and Pete Rouse, his Senate chief of staff.

In turning to Mr. Emanuel and Mr. Podesta, Mr. Obama sought out two of the hardest-hitting veterans of President Bill Clinton’s administration, known for their deep Washington experience, savvy and no-holds-barred approach to politics. Neither is considered a practitioner of the “new politics” that Mr. Obama promised on the campaign trail to bring Republicans and Democrats together, suggesting that the cool and conciliatory new president is determined to demonstrate toughness from the beginning.