Harris and Beau "spoke on the phone practically every day" when they were the attorney generals of California and Delaware

Kamala Harris Beau Biden
Sen. Kamala Harris (left) and Beau Biden
| Credit: Alexander Tamargo/Getty; Paul Drinkwater/NBCU Photo Bank/NBCUniversal via Getty

Kamala Harris took a moment during her first appearance with running mate Joe Biden to pay tribute to the presidential candidate's late son, Beau Biden.

Harris, 55, was friends with Beau when they were both attorneys general in California and Delaware, respectively.

"Ever since I received Joe’s call, I've been thinking about the first Biden I really came to know — Joe’s son, Beau," Harris said during her speech in Wilmington, Delaware, on Thursday in the first joint appearance with Biden since he named her his vice presidential pick.

"In the midst of the Great Recession, Beau and I spoke on the phone practically every day, sometimes multiple times a day, working together to win back billions of dollars for homeowners from the biggest banks in the nation that were foreclosing on people’s homes," Harris remembered.

"And let me tell you about Beau Biden," she continued. "I learned quickly that Beau was the kind of guy who inspired people to be a better version of themselves."

"He was the best of us," she said of Beau, who died in 2015 of brain cancer at age 46.

2008 Democratic National Convention: Day 3
Beau Biden at the Democratic National Convention in 2008
| Credit: Mark Wilson/Getty
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Sen. Kamala Harris speaking in Wilmington, Delaware, on Wednesday after being named Joe Biden's running mate
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The elder Biden acknowledged Harris' friendship with his late son as well on Tuesday when he announced the prosecutor-turned-lawmaker would be his running mate in the 2020 election against President Donald Trump.

"I watched as they took on the big banks, lifted up working people, and protected women and kids from abuse," Biden tweeted. "I was proud then, and I'm proud now to have her as my partner in this campaign."

Biden noted Harris and Beau's history again Wednesday in his own speech before introducing Harris — with their twin set of remarks doubling as backstory on Harris and a set of criticisms of the Trump administration they hope to beat. (The Trump campaign has been quick with its own attack ads.)

"My campaigns have always been family affairs," Biden said Tuesday, noting: "Here’s the best part: Kamala, you’ve been an honorary Biden for quite some time."

Biden pointed out that Beau had long "respected Kamala and her work."

"That mattered a lot to me as I made this decision," Biden said.

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From left: Beau Biden and Kamala Harris
| Credit: Kamala Harris/Twitter

The former vice president and his wife, Former Second Lady Dr. Jill Biden, have had Beau on their mind throughout 2020.

The couple held a private memorial service in late May to mark the fifth anniversary of his death.

Beau had survived the 1972 car accident that killed his mother — Biden's first wife, Neilia Hunter — and the couple's 1-year-old daughter, Naomi. Beau and his younger brother, Hunter, survived.

Just before the fifth anniversary of Beau's death, Biden told Late Show host Stephen Colbert that his son has been in the back of his mind since launching his 2020 campaign last April.

"Every morning I get up, I ask myself, 'Is he proud of me?' Am I meeting the requirement that I promised him that I would do?" Biden told Colbert, adding that Beau was his "soul" and that Hunter was his "heart."