Presumptive Democratic White House nominees Joe Biden and Kamala Harris made their first public appearance together since Tuesday’s announcement that the California senator was chosen as Biden’s running mate.

Watch the Biden-Harris appearance here:

The former primary rivals appeared at the Alexis I. duPont High School gymnasium in his hometown of WIlmington, Delaware, to discuss their vision on how to defeat President Donald Trump this fall and then lead the country through a pandemic, its economic fallout and protests over racial injustice.

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Harris, Biden said, is “smart, she’s tough, she’s experienced, she’s a proven fighter for the backbone of this country.”

“Kamala knows how to govern. She knows how to make the hard calls. She’s ready to do this job on day one,” he continued.

Biden spoke of her experience questioning Trump administration officials in the Senate, and highlighted the historic nature of her pick, noting she's the daughter of immigrants from India and Jamaica,

“This morning, all across the nation, little girls woke up -- especially little black and brown girls, who so often feel overlooked and undervalued in their communities. But today, today, just maybe, they’re seeing themselves for the first time in a new way,” Biden said.

Harris sat feet away from Biden, listening with her mask off.

Taking the stage after him, Harris said she was “mindful of all the ambitious women before me, whose sacrifice, determination and resilience makes my presence here today even possible.” She then launched into an attack on Trump, lambasting him for a lack of leadership on the coronavirus pandemic.

“This is a moment of real consequence for America. Everything we care about — our economy, our health, our children, the kind of country we live in — it’s all on the line,” she said.

Harris and Biden were scheduled to sit down together for an online fundraiser designed to let donors get a glimpse of what the Democratic presidential ticket will look like together.

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The Biden campaign has said it plans a rollout that blends the historic nature of Harris’ selection with the realities of the 2020 campaign and the gravity of the nation’s circumstances.

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“I need someone working alongside me who is smart, tough and ready to lead. Kamala is that person,” Biden told his supporters in an email explaining his running mate choice.

“I need someone who understands the pain that so many people in our nation are suffering. Whether they’ve lost their job, their business, a loved one to this virus,” Biden continued. “This president says he doesn’t want to be distracted by it. He doesn’t understand that taking care of the people of this nation – all the people – isn’t a distraction; it’s the job. Kamala understands that.”

»MORE: Inside Joe Biden’s search for a running mate

Harris was considered a favorite throughout Biden’s search. She’d been a regular surrogate for him for months, with the pair appearing at ease during online fundraisers together and the senator appearing on her own as a surrogate for campaign events and on television.

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They’ll nonetheless have to paper over some differences exposed during the early primary campaign, from Harris’ initial support for a single-payer health insurance system and the Green New Deal to her deeply personal debate-stage broadside against Biden over his opposition to federally mandated busing to integrate public schools in the 1970s.

Trump’s campaign immediately seized on those circumstances, with the president tagging Harris as “Phony Kamala” and casting her as the latest evidence that Biden, a five-decade veteran of the Democratic establishment, is captive to “the radical-left.”

Harris, like Biden, doesn’t support a single-payer health insurance system, and the two are broadly considered part of the Democratic Party’s mainstream. But Harris memorably raised her hand during one Democratic primary debate when candidates were asked whether they could back a system that scrapped private health insurance altogether.

She has broadly endorsed the Green New Deal, progressives’ most ambitious set of proposals to combat the climate crisis, but she didn’t make that an anchor of her presidential bid. Biden has moved left on his climate proposals during the 2020 campaign but has not fully embraced the Green New Deal.

»MORE: Shaun King, who bashed Harris during campaign, explains why he is now ‘incredibly proud’ of her

In Washington, Harris has advocated overhauling the criminal justice system, intensifying her efforts since George Floyd’s death while in Minneapolis police custody in May. And she’s called for sweeping domestic programs to benefit the working and middle class. But she has taken heat for some of her aggressive stances as a local prosecutor in the San Francisco area and for not prosecuting bank executives in the wake of the 2008 financial collapse.

The Associated Press contributed to this report.