Democratic Sen. Dianne Feinstein of California was poised to become president pro tempore of the Senate, according to long-standing Senate tradition.

As a result of her new status as the longest-serving Democratic senator, the 89-year-old lawmaker would have been third in line to the presidency, behind the vice president and House Speaker.

But Feinstein — who will also be the chamber's oldest currently-serving member come January — issued a statement to the Washington Post last month saying that she's not interested in running for and serving as president pro tempore of the Senate.

Senate Majority Leader Chuck Schumer will instead nominate the 72-year-old Democratic Sen. Patty Murray of Washington — the next most senior Democratic senator, having been elected just two months after Feinstein — to the position, a source familiar with the discussions told Insider on Wednesday.

Yet when Feinstein was asked by Insider at the Capitol on Tuesday about the potential of taking on the job — she would be the first woman in American history to hold the position — the California Democrat insisted that she hadn't thought about it.

"Well, I haven't thought about it, but I'll let you know when I do," said Feinstein, who was first elected in 1992. "I just got back, I've had a lot of issues."

An aide walking with the senator quickly interjected, telling Insider that Feinstein had "told a few reporters in the past that she's not thought about it, and has no intention of seeking the position."

"That's what you've told reporters," the aide said to Feinstein.

"I don't know what you're saying," she replied.

"This is about the Senate pro tem position," he said.

"Well, I haven't said anything about it, that I know of," she insisted.

"You were asked about it over the break, and you put out a statement saying that you had no intention of running for it," he said, apparently referencing the statement given to the Post.

"Okay, well then, I guess it's out," she conceded.

Asked by Insider why she doesn't want the position, she pointed to her husband's recent death.

"I just lost my husband a short time ago, I'm putting my life together, and I intend to continue in this position and do as well as I possibly can," she said.

But the lawmaker refused to say she wasn't up to the job.

"I'm just saying I haven't thought about it."

The California Democrat's apparent decision not to seek the position comes amid ongoing questions about her ability to serve given both her age and reports that she is experiencing cognitive decline. Earlier this year, Senate Majority Leader Chuck Schumer declined to say whether he had confidence in her ability to serve when asked by Insider.

Feinstein has at times appeared confused when performing routine duties as a legislator.

"I don't even know what that is," an exasperated Feinstein could be heard telling a staffer in the Capitol about a vote on a government funding bill in September.

After facing criticism from fellow liberals for her handling of Supreme Court Justice Amy Coney Barrett's confirmation hearing in the fall of 2020, Schumer reportedly had to tell Feinstein on two separate occasions to step down as the top Democrat on the committee, which she agreed to do.

Schumer announced his nomination of Murray — which will be voted on by the Democratic caucus on December 8 — during the party's closed-door Senate caucus lunch on Wednesday, according to the source.

The day before, Insider attempted to ask Murray if she would seek the position at Senate Democrat's weekly Tuesday press conference. But Schumer quickly interjected."Stay tuned," he said.

Insider recently explored America's gerontocracy in the "Red, White, and Gray" project, finding that nearly one in four members of Congress are in their 70s and 80s and that the vast majority of Americans view the increasingly advanced age of politicians as a problem. And staffers for long-serving members have often had to play an outsize role in helping their bosses do the job.