(CNN) - With Sen. Hillary Clinton's presidential campaign officially over, she is focusing on making sure her supporters back Sen. Barack Obama's bid.
Throughout the primary season, Clinton and Obama expressed confidence the Democrats would unify once a nominee emerged.
As Clinton closed her campaign Saturday, she urged the cheering crowd of thousands to support Obama in his run for the White House, saying she and supporters should "take our energy, our passion and our strength and do all we can to help elect Barack Obama ... I ask all of you to join me in working as hard for Barack Obama as you have for me."
Her endorsement was met with a scattering of boos and thumbs downs from the crowd at the National Building Museum in Washington.
In a CNN poll released Friday, 60 percent of Clinton supporters said they would vote for Obama, but 17 percent said they would vote for McCain and 22 percent, said they would not vote at all if Clinton were not the nominee.