The American Federation of Labor and Congress of Industrial Organizations has thrown its unanimous support behind Kamala Harris in the 2024 presidential race.

"From day one, Vice President Kamala Harris has been a true partner in leading the most pro-labor administration in history," AFL-CIO President Liz Shuler wrote in a statement Monday.

"At every step in her distinguished career in public office, she’s proven herself a principled and tenacious fighter for working people and a visionary leader we can count on," Shuler continued.

"From taking on Wall Street and corporate greed to leading efforts to expand affordable child care and support vulnerable workers, she’s shown time and again that she's on our side. With Kamala Harris in the White House, together we'll continue to build on the powerful legacy of the Biden-Harris administration to create good union jobs, grow the labor movement and make our economy work for all of us," she added.

The support for Harris' campaign comes as some of the nation's largest unions also have offered support, praise and outright endorsements to the vice president.

The Service Employees International Union, whose 2 million members make it the nation's largest private sector union, endorsed Harris on Sunday. So did Local 3000 of the United Food and Commercial Workers, a labor organization in the Pacific Northwest, which drew attention last week when it became the only Biden-aligned union to call for him to step aside.

-ABC News' Beatrice Peterson and Max Zahn

Vice President Kamala Harris thanked President Joe Biden for endorsing her in the 2024 presidential race on Monday.

"It is my great honor to have Joe's endorsement in this race," Harris said while speaking to campaign staff in Delaware.

Echoing Biden's comments on his commitment to the Democratic campaign, Harris said, "Joe is not done, far from it."

"He knows there is still more work to do and our nation will continue to praise his bold and visionary leadership as president," Harris said, adding, "Thank you, Joe."

-ABC News' Gabriella Abdul-Hakim, Fritz Farrow and Will McDuffie

President Biden called in to speak with Kamala Harris' campaign HQ on Monday, saying he "isn't going anywhere" after announcing Sunday that he's stepping aside from his reelection bid.

"The name has changed at the top of the ticket, but the mission hasn't changed at all," Biden said over the phone. "And by the way, I'm not going anywhere. I'm going to be out there on the campaign with her," he added.

"I'm going to be working like hell, both as a sitting president, getting legislation passed, as well as in campaigning," Biden said.

-ABC News' Gabriella Abdul-Hakim, Fritz Farrow and Will McDuffie

Kentucky Gov. Andy Beshear said he spoke to Vice President Kamala Harris after her campaign announcement Sunday.

"The vice president reached out to me yesterday, just a couple hours after the president put out the news, and I was very grateful that she would reach out to me personally. She asked for my support. I agreed, and thus, this morning, I fully endorsed her and will do everything I can to help her win," Beshear told Louisville ABC affiliate WHAS.

Amid speculation Beshear could be a possible running mate, the governor signaled what he could bring to the campaign.

"We've shown that we know how to win. We know how to reach across the divide, and how to campaign in a way where we talk to people and not at them, where we listen to people's concerns and we give them confidence that we're going to address them," Beshear said.

"But I think it's more than just running," Beshear added. "It's also how you govern, governing in a way that addresses people's everyday needs, the things they worry about when they get up in the morning,” he said.

-ABC News' Jacob Steinberg