President Barack Obama endorsed Hillary Clinton for president in a recorded statement (video below).
"I know how hard this job can be. That's why I know Hillary will be so good at it. In fact, I don't think there's ever been someone so qualified to hold this office," he said in the video, which was posted on YouTube.
Obama added: "I'm with her. I am fired up, and I cannot wait to get out there and campaign for Hillary."
The endorsement adds a chapter to the long history between Obama and Clinton, which began with their testy 2008 primary battle.
In a 2008 campaign ad, Obama accused Clinton of lying and attacked her record on NAFTA and her vote for the Iraq War.
"Hillary Clinton will say anything and change nothing," the ad stated.
But in the video endorsement, Obama praised Clinton's acceptance of his invitation to join his cabinet.
"Even after our own hard-fought campaign, in a testament to her character, she agreed to serve our country as Secretary of State," he said.
After the video was released, a bit of a Twitter spat erupted between Clinton and presumptive Republican nominee Donald Trump.
“Obama just endorsed Crooked Hillary. He wants four more years of Obama—but nobody else does! “ tweeted Trump.
In response, Clinton quoted Trump's tweet and replied, “Delete your account.”
That tweet went viral, but didn't stop Trump from responding.
"How long did it take your staff of 823 people to think that up - and where are your 33,000 emails that you deleted?" he shot back.
With Obama's endorsement, Sanders is the last major Democratic figure with a national following who has yet to back her bid for the White House. However, the Vermont Senator has vowed to help her defeat Trump in the general election.
"I look forward to meeting with [Clinton] in the near future to see how we can work together to defeat Donald Trump and to create a government which represents all of us and not just the 1 percent," Sanders said, according to CNN.