Former President Barack Obama has also endorsed Vice President Harris.
Vice President Kamala Harris wrapped up what has been a whirlwind week in the presidential race with her campaign saying Sunday it has raised more than $200 million in less than a week.
On Thursday night, Harris met with Israeli Prime Minister Benjamin Netanyahu and took the lead in addressing the public about their discussions.
Harris has secured commitments from enough delegates to become the presumptive nominee if they all honor their commitment when voting, according to ABC News reporting.
About 500 White House staffers will be gathered together tonight to watch President Biden's remarks from the White House State Floor, which includes the East Room and State Dining Room.
Just before 7 p.m., there was a procession of staffers making their way over from the Eisenhower Executive Office Building, where most staffers work, to the White House North Portico entrance.
-ABC News' Karen Travers
Donald Trump is currently holding a rally in Charlotte, North Carolina -- his first since Biden dropped out of the race.
The former president quickly turned his focus to Harris, claiming she is "the ultra-liberal driving force behind every single Biden catastrophe."
"You know, I was supposed to be nice," Trump said. "They say something happened to me when I got shot, I became nice. And when you're dealing with these people, they're very dangerous people. When you're dealing with them, you can't be too nice. You really can't be. So, if you don't mind, I'm not going to be nice."
"The defense of democracy is more important than any title," Biden will say in his prime-time address tonight, according to excerpts released by the White House. "I draw strength, and find joy, in working FOR the American people. But this sacred task of perfecting our Union is not about me. It’s about you. Your families. Your futures. It’s about 'We the People.'"
He will go on to praise America as a place where "kings and dictators do not rule" -- perhaps a subtle jab at Donald Trump, who once remarked he would be a dictator only on "Day 1" if elected to a second term.
"The great thing about America is here, kings and dictators do not rule. The people do," Biden will say. "History is in your hands. The power is in your hands. The idea of America – lies in your hands."
-ABC News' Molly Nagle
In his Oval Office address later this evening, Biden will discuss his decision to withdraw from the 2024 race and endorse Vice President Kamala Harris.
"I have decided the best way forward is to pass the torch to a new generation. That is the best way to unite our nation," he will say, according to excerpts of his speech released by the White House.
He will also reiterate his commitment to seeing out the remainder of his term.
"Over the next six months I will be focused on doing my job as president," he will say. "That means I will continue to lower costs for hard-working families and grow our economy. I will keep defending our personal freedoms and our civil rights – from the right to vote – to the right to choose."
-ABC News' Molly Nagle
