WASHINGTON - Surrounded by several thousand supporters, Sen. Hillary Rodham Clinton today formally suspended her 2008 quest of the presidency, throwing "my whole support" to her party's presumptive nominee, Sen. Barack Obama, and even voicing his campaign's signature motto.

"Today," she said, "I am standing with Sen. Obama to say, 'Yes, we can!' "

While most of her listeners responded with cheers, there were scattered boos each time that she pledged her backing to her former rival.

Clinton's concession came in the soaring atrium of the National Building Museum, with her enthusiastic and emotional backers arrayed in front of her, behind her, and above her on the double-decked balconies that ring the space.

She delivered her speech four days after Obama went over the top, surpassing the 2,118 delegates needed to secure the Democratic nomination.

On Tuesday night, in the wake of the final primaries, the New York senator had declined to acknowledge her rival's victory and had seemed to hold out the possibility of continuing the fight in one way or another.

There was none of that today. Clinton was gracious and supportive, telling the crowd in the hall and those watching on television that she would "work my heart out for Sen. Obama."

In addition, she hailed her accomplishment as the first woman to come so close to winning a major-party nomination, saying that she and her supporters have paved the way for a woman to become president.