Sen. Dianne Feinstein participates in a reenacted swearing-in with her husband Richard Blum and Vice President Joe Biden on January 3, 2013 in Washington, DC.
CNN  — 

President Joe Biden hailed the late Sen. Dianne Feinstein as a “pioneering American” and a “true trailblazer” in a statement Friday following her death.

“Dianne made her mark on everything from national security to the environment to protecting civil liberties. She’s made history in so many ways, and our country will benefit from her legacy for generations,” Biden wrote in a statement about the California Democratic senator.

Biden often speaks nostalgically about his time in the Senate, describing those years as having been marked by a kind of decorum and civility missing in politics today. Feinstein was a stalwart of his tenure on Capitol Hill, and the two shared a bond on policy and politics, especially on the Judiciary Committee and gun control efforts.

Harkening to the 15 years they served together in the Senate, Biden said he had a “front row seat to what Dianne was able to accomplish.”

Biden and Feinstein served as colleagues in the Senate for 15 years, from when she was elected in 1992 to Biden’s election as vice president in 2008. She became the first woman to serve on the Senate Judiciary Committee in 1993, when Biden was serving as the panel’s chairman, and has credited him with assigning her to the post.

“Often the only woman in the room, Dianne was a role model for so many Americans – a job she took seriously by mentoring countless public servants,” Biden said Friday. “Dianne was tough, sharp, always prepared, and never pulled a punch, but she was also a kind and loyal friend, and that’s what [First lady] Jill and I will miss the most.”

Feinstein, along with Biden, championed an assault weapon ban in 1994 as part of a larger crime bill under then-President Bill Clinton. Now expired, the assault weapon ban remains a priority of Biden’s as he works to advance new gun controls.

When calling on lawmakers to get to work on passing gun control measures, Biden in recent months pointed to his work as a senator with Feinstein on passing the assault weapons ban.

Feinstein served as chair of the inaugural committee in 2009, placing her next to Biden for much of the day’s activities as he was sworn in as vice president.

The announcement of Feinstein’s death comes one day after Biden paid tribute to another close friend from his career in the Senate: the late Arizona Republican Sen. John McCain.

In a speech in Arizona about defending democracy, Biden on Thursday said he had recently been thinking about “how much America missed John right now, how much America needed John’s courage and foresight and vision.”

Early backing of Biden’s presidential bid

When Biden was considering his own run for president, Feinstein voiced early support for his presidential bid after a private meeting.

“He made me the first woman on the Judiciary Committee 26 years ago, and I’ve never forgotten it,” Feinstein previously said at the time, referring to the former Delaware senator’s tenure atop the panel. “I’ve known him, I’ve worked with him and it’s just a logical step for me.”

Later, she held a fundraiser for Biden along with her husband, Richard Blum, in San Francisco, and there was later speculation Biden would name Blum to an ambassadorship in Europe.

At one point, Feinstein even dismissed the candidacy of his rival for the 2020 nomination, then-California Sen. Kamala Harris, suggesting she was “brand new” in the Senate at the time.

The White House treaded carefully when asked about widespread concerns about Feinstein’s health and her ability to continue serving in the Senate and did not publicly weigh in on discussions about a potential replacement.

Those questions came as close advisers have been batting away concerns about the president’s own age and defending the 80-year-old’s stamina and endurance ahead of the 2024 election.

This story has been updated with additional developments.