The San Francisco Chronicle reported on Thursday that four US Senators witnessed Sen. Dianne Feinstein's memory rapidly degrading. Three former staffers spoke to the Bay Area outlet and said they were concerned about the 88-year-old's cognitive abilities.

There is a major threat to the Senate Democratic majority.

If one of the six senators were to step down, the Republican governor of that state would have the power to appoint a temporary replacement.

If any of them were to leave the Senate before November because of a retirement, health issue, or other reason, the Democrats could lose their control of the chamber and doom President Joe Biden's chances of getting major agenda items done this year.

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Sen. Bernie Sanders of Vermont arriving at the Capitol on October 20.
Stefani Reynolds/Getty Images

There is concern about the advanced age of powerful senators. Capitol Hill reporters have seen it up close as they interact with lawmakers who have been in Washington for decades.

The Washington establishment was frightened when Capitol Hill doctors told Sen. Patrick Leahy to go to the hospital. The Vermont Democrat said that he intended to serve the remaining two years of his term and that he was fine.

Concerns over the Democrats ability to accomplish agenda items that their increasingly young and diverse base commands have cast new light on an aging Senate that, like the rest of the world, is more susceptible to the detrimental and deadly health effects of COVID-19.

The idea that control of the United States Senate is dependent on the medical care of a couple of very well-intentioned and highly capable senior citizens is not the way the government should function, according to a former Hillary Clinton staffer.

It is difficult to have a conversation in a public space with so many powerful people.

Representatives for the six senators and Majority Leader Chuck Schumer did not respond to questions from Insider.

An inconvenient map

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Sen. Joe Manchin in February 2020.
Photo by Sarah Silbiger/Getty Images

In the midst of his presidential campaign, the 81-year-old independent from Vermont had a heart attack. Vermont's governor, Phil Scott, is a Republican, but he is moderate. Scott said last year that he would appoint another independent, potentially left-leaning, if Biden were to pick a cabinet that was left-leaning. Senate control is still uncertain.

In November 2021, he said he wouldn't seek another term in office.

Massachusetts is where the Republican Charlie Baker runs the executive.

Governors in Vermont and Massachusetts can name temporary replacements until a special election is held. Special elections can upend expectations.

Scott Brown shocked the country in 2010 when he won a special election to fill the seat of the late Ted Kennedy. Democrats had been able to move bills along party lines without fear of a GOP-led filibuster if Brown had won.

West Virginia, a majority-Democratic state during the past century that has seen its politics shift to the right, is where Joe Manchin comes from. Jim Justice, a Democrat, switched his party affiliation to Republican during an event with President Donald Trump.

Chris Sununu was elevated to the governor's mansion by the voters of New Hampshire. The governor in both states can appoint a replacement for the Senate until the term of the ex-incumbent ends. If Maryland's Republican governor, Larry Hogan, left office early, he would have to name a replacement from the same party as Ben Cardin.

This is not an abstract concern

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Sen. Jeanne Shaheen after winning reelection in 2020.
AP Photo/Charles Krupa

Matters of illness or death are not an abstract concern for the Senate, despite the fact that these senators have not recently disclosed any plans or conditions that would render them incapable of finishing their terms.

The chamber has had senators dying in office since 1789. 301 senators have died before finishing their terms. The first person to die was William Grayson. John McCain was 80 years old when he died from brain cancer, which he had been diagnosed with. Arizona elected a Democrat to replace him.

Illness and injury have ended other careers. The late Senate Majority Leader HarryReid retired after a serious accident when he was 75 that involved an exercise band and a bad fall.

'You never know what tomorrow will bring'

The Senate has a delicate balancing act that could cause problems for other members if they couldn't finish out their term.

Nine Republican senators represent states with a Democratic governor who would be able to replace them with someone from the opposing party. Senate Minority Leader McConnell is 80.

Several Democrats younger than 70 come from states where a Republican executive could replace them. The group includes two new senators from Georgia, Raphael and Jon Ossoff, as well as Sen. Jon Tester of Montana, who is 65 years old.

Both North Carolina and Arizona have governors of the opposite party as their senators, but state laws require their governors to appoint a senator from the same party as the vacating incumbent.

Among the older crowd of Democrats, there are no plans to leave before their term ends or to step down.

Democrats acknowledge there is no room for error or early exits as they navigate the Senate.

Barbara Boxer, a California Democrat who announced her retirement in 2015 at the age of 74, told Insider in a phone interview. Yes. Is power shaky? Yes. What is the answer? Do what you can when you can.

The story was originally published on February 3, 2021.