The choice of Mrs. Clinton pleased many in the Democratic establishment who admire her strength and skills, and they praised Mr. Obama for putting the rancor of the campaign behind him. “Senator Clinton is a naturally gifted diplomat and would be an inspired choice if she is chosen by President-elect Obama as secretary of state,” said Warren Christopher, who held that job under her husband.

But it could also disappoint many of Mr. Obama’s supporters, who worked hard to have him elected instead of Mrs. Clinton and saw him as a vehicle for changing Washington. Mr. Obama argued during the primaries that it was time to move beyond the Clinton era and in particular belittled her claims to foreign policy experience as a first lady who circled the globe.

Advisers said Mr. Obama concluded after the election that the problems confronting the nation were so serious that he needed Mrs. Clinton’s stature and capabilities as part of his team, notwithstanding their past differences. The bitterness that inhabited the Obama team for much of the year has faded with time, advisers said.

And many of the aides working on the transition with Mr. Obama are not campaign veterans with scars from the primaries, but rather former Clinton administration officials like Rahm Emanuel, the incoming White House chief of staff, and John D. Podesta, the transition co-chairman, who admire Mrs. Clinton.

For Mrs. Clinton, becoming secretary of state would require her to sacrifice the independence that has come with a Senate seat and the 18 million votes she collected in the primary season. She has found it liberating the last eight years to speak for herself, not as someone’s spouse. But friends said she could still have her voice while subordinating her ambitions to Mr. Obama’s agenda.

“Hillary Clinton will always be seen as her own person,” said Mickey Kantor, a longtime friend who served as commerce secretary in her husband’s administration. “But you know, Hillary Clinton’s a terrific lawyer. She knows how to represent a client, and she’s good at it. And I don’t have any doubt in my mind that she’ll be a team player.”

Mrs. Clinton had to accept that she might never become president, a former aide said. “There’s a very small chance that she could run again,” he said. “You’re not going to be the president, so you want to make sure your next few years, which may be your last in public life, really make a mark.”