June 7, 2008— -- Sen. Hillary Clinton conceded the Democratic nomination to Sen. Barack Obama Saturday in Washington.
"The way to continue our fight now, to accomplish the goals for which we stand, is to take our energy, our passion, our strength, and do all we can to help elect Barack Obama as the next president of the United States," Clinton said.
"Today, as I suspend my campaign, I congratulated him on the victory he has won. ... I endorse him and throw my full support behind him."
Clinton began lightly, telling the cheering crowd, "Well, this isn't exactly the party I'd planned, but I sure like the company."
Thousands gathered at the National Building Museum as Clinton thanked supporters, formally endorsed Obama and urged Democrats to unite behind him in an effort to defeat presumptive Republican nominee Sen. John McCain in November.
"I have seen his strength and determination, his grace and his grit," Clinton said, as she called for her supporters to fall in line behind Obama's nomination.
"We may have started on separate journeys but today our paths have merged and we're all heading toward the same destination."
"Today I am standing with Sen. Obama to say, 'Yes, we can!' " Clinton said.
For many Clinton supporters -- particularly women who had hoped the former first lady would become the nation's first female presidential nominee of a major party -- the end is difficult to accept.
"I'm heartbroken," said Arnica Fisher, who got up at 3 a.m. to road trip from Redding, Pa., to be at the speech.
"You physically feel it," she added, with tears welling in her eyes.
Clinton made gender a central theme of her concession speech.
"I ran as a daughter who benefited from opportunities that my mother never dreamed of. I ran as a mother who worries about her daughter's future," Clinton said. "To build that future we must understand that women and men alike understand the struggles of their mothers and grandmothers."
"Although we weren't able to shatter that highest, hardest glass ceiling, thanks to you it's got about 18 million cracks in it and the light is shining through like never before," she said.
Clinton invoked the suffragists who fought for women's right to vote and civil rights leaders who advocated on behalf of equal rights for African-Americans as she insisted, "The path will be a little easier next time ... that has always been the history of progress."
It's a dramatic end to one of the longest, most closely fought primary races in recent history, and one that is unbelievable to many of Clinton's most ardent supporters.
"I don't think that it has completely set in yet," said Karen Defilippi, 25, a Clinton supporter who quit her job at a university in Washington last August to work for Clinton's campaign in Iowa and other primary states.
Defilippi, who is now out of a job, defended Clinton's decision to wait until Wednesday to acknowledge Obama's victory.
"It was just a little too soon for people," said Defilippi. "Her supporters are strong supporters, and I don't think they were ready to accept it."
The line to enter the National Building Museum in Washington stretched around the block, many supporters are from the area, but some drove in from out of state.
Some say it's time for the party to move on and they'll follow Clinton's marching orders.
"If we supported her and she supports him -- we support him," said Kevin Hostetler, 23, of Arlington, Texas.
Some were already Obama fans and are just here to witness the end of Clinton's run. But for others, no matter what Clinton says in her concession to her rival, they will never back Obama.
Rosemary Storaska of Stafford, Va., volunteered for Clinton, following the campaign all over Pennsylvania. Citing what she sees as Obama's severe lack of experience, she said she will vote for John McCain.
"I worked on her campaign since Thanksgiving. ... That is the one place we won't follow her."
Dee Sawyers made sure she was first in line to hear Clinton's speech Saturday.
"I think we'll look back at this race and see what was truly historic about it," she said.
Sawyers said even though Clinton isn't making it all the way to the White House, her 25-year-old daughter and a generation of young women have been shown that it is possible for a woman to make it in politics.
"It's not for the faint of heart," she said.
Clinton hosted a big bash for her staff Friday at the Clintons' home in Washington.
"There's no booze! I'll fix that," joked Terry McAuliffe, Clinton's campaign chairman.
Inside, Clinton thanked her dedicated staff for putting their lives on hold. Former President Bill Clinton and daugther Chelsea Clinton were at her side but did not speak Saturday.
"My mother wants it to be very clear that we are all going to unite our party and take back the White House in November!" Chelsea Clinton told Democrats at a prescheduled Democratic party fundraiser Friday night.
At a secret, one-hour meeting at the home of Clinton supporter Sen. Dianne Feinstein, D-Calif., Thursday night, Clinton and Obama sat down face-to-face for the first time since the end of the nomination contest.
The rivals agreed it's not helpful to have Clinton supporters pushing Obama to make her the vice presidential running mate.
"I saw Bill go through this. And I know this has to be your decision," Democratic sources said Clinton told Obama.
The meeting, Feinstein says, was a good first step toward brining the Democrats back together.
No matter how civil, how courteous you tend to believe your opponent, in a campaign, you get rubbed a little raw, its hard, you need some recovery for those raw spots," Feinstein said.
For her part, Clinton asked her supporters to look forward, not backward.
"Every moment wasted looking back keeps us from going forward," said Clinton. "Life is too short, life is too precious, and the stakes are too high to dwell on what might have been. … I will work my heart out to make sure Barack Obama is our next president.
ABC News' Jennifer Parker and Ed O'Keefe contributed to this report.