Former Vice President Joe Biden described Sen. Kamala Harris, D-Calif., as “experienced,” a “proven fighter” and ready to handle the presidency on day one of a Biden administration in their first joint appearance as a presidential ticket in Wilmington, Delaware, Wednesday evening.

Introducing Harris, Biden praised the senator’s bonafides and and took aim at President Donald Trump a day after the presumptive Democratic presidential nominee announced his selection of Harris as his running mate.

Biden said Harris “knows how to govern, knows how to make the hard calls” and is “ready to do this job on day one.”

When she stood to speak, Harris said she was “incredibly honored by this responsibility” and said the Democratic primary provided the country a “resounding message — that Joe was the person to lead us forward.”

She thanked “ambitious women before me” who helped to pave the path for her and called the present moment one “of real consequence for America,” pointing to the coronavirus crisis and social justice efforts.

Blasting Trump and his administration, Harris said the case against a second Trump term is “open and shut.”

“In just 83 days, we have a chance to choose a better future for our country,” she said.

“America is crying out for leadership,” Harris added. “Yet we have a president who cares more about himself than the people who elected him, a president who is making every challenge we face more difficult to solve.”

Biden pointed to Harris’ record on guns, the environment, banking and LGBTQ issues, and said she went “toe to toe” with Trump officials in congressional hearings who were “trying to hide the truth.”

Noting Harris’ membership on the Senate Intelligence and Judiciary committees, Biden said “she’s been in the middle of the most critical national security challenges our country faces.”

As a result, Harris is “well aware of the threats to this nation and how to respond to them,” he added.

Harris is the first Black or Asian American woman to appear on a major party presidential ticket. Biden said that Harris’ experience growing up was different from his, but “not so different in the essentials.”

“She’s worked hard, never backed down from a challenge and earned each and every accolades and achievements she’s gained,” Biden said.

Biden said he asked Harris “to always be the last voice in the room” with him on major decisions.

Both Biden and Harris spoke of the senator’s relationship with Biden’s eldest son Beau, the former Delaware attorney general who died in 2015 of brain cancer. Biden said he first got to know Harris through his son.

“I know how much Beau respected Kamala and her work,” he said. “And that meant a lot to me, to be honest with you.”

Harris spoke of her work with Biden’s son during the financial crisis while both were state attorneys general, saying, “I learned quickly that Beau was the kind of guy who inspired people to be a better version of themselves.”

Biden chose Harris after a lengthy deliberation that featured a number of prominent contenders, like former national security adviser Susan Rice, Michigan Gov. Gretchen Whitmer, Rep. Karen Bass, D-Calif., and Sens. Tammy Duckworth, D-Ill., and Elizabeth Warren, D-Mass.

The former vice president said those under consideration are “talented women leaders, all of them qualified to be president,” and he thanked them for being part of the process.

One-time rivals in the 2020 Democratic presidential primary campaign, Harris and Biden delivered remarks outlining their campaign themes as they take on Trump and Vice President Mike Pence ahead of the fall election.

Trump has already taken swipes at Harris after the announcement and said he was “a little surprised” Biden chose her.

In his speech, Biden hit back at Trump, saying “whining” is his greatest skill.

“Whining is what Donald Trump does best,” Biden said. “Better than any president in history.”

Biden’s selection of Harris as his running mate was praised by prominent Democrats, including former President Barack Obama, who said in a statement that Biden “nailed this decision.”

“By choosing Senator Kamala Harris as America’s next vice president, he’s underscored his own judgment and character,” Obama said. “Reality shows us that these attributes are not optional in a president. They’re requirements of the job. And now Joe has an ideal partner to help him tackle the very real challenges America faces right now and in the years ahead.”