That gnashing sound you hear are the political gears shifting in response to Dianne Feinstein’s announcement – after months of delay – that she’ll seek another U.S. Senate term next year.

“I am running for reelection to the Senate,” Feinstein declared on Twitter Monday morning. “Lots more to do: ending gun violence, combating climate change, access to healthcare. I’m all in!”

All in? Maybe, but clearly she agonized for months over whether, at 84 and with her husband, wealthy investor Richard Blum, in poor health, she really wanted another campaign and another six years in a Republican-controlled Senate.

Democratic Party leaders were urging her to run. The party has three dozen Senate seats up next year and will be stretched thin to defend those in red states. They didn’t want an all-out contest in California that would keep her seat in Democratic hands, but soak up many millions of campaign dollars.

However, some leading Democratic politicians were, albeit secretly, hoping Feinstein would, after a quarter-century in the Senate, hang it up and give them a shot at a potential steppingstone to the White House. After all, Kamala Harris was being touted as presidential material even before she had adjusted her chair on the Senate floor.

Now ambitious, relatively young politicians, such as Senate President Pro Tem Kevin de León, must decide whether to continue waiting for another opening, elbow into the already crowded field for the governorship or gamble on challenging Feinstein.

De León’s situation is particularly dicey because he’ll be forced out of the Legislature next year by term limits and doesn’t have an office to occupy while he waits.

Feinstein’s overall standing among California voters remains fairly high – a 50 percent approval rating in an early September Berkeley IGS Poll – but that was down from 59 percent in March, dropping her below Harris. And a recent Public Policy Institute of California poll found that half of voters said she should retire.

Feinstein’s falloff reflects mounting criticism from the Democratic Party’s left wing that she’s been too moderate and too easy on President Donald Trump, and a generational divide. Her support among under-40 voters in the Berkeley IGS Poll was well under 50 percent.

Feinstein’s re-election announcement sparks two questions that only time will answer:

–Although a challenge from the left is likely, will it be serious by a well-known, well-financed rival such as de León or billionaire environmentalist Tom Steyer, or just a token candidate?

–And if, as likely, Feinstein does win another six-year term next year, will she continue until 2024, when she will be 91?

One theory bouncing around in political circles is that she reluctantly agreed to run again but is likely to retire sometime after winning, touching off a feeding frenzy for an appointment by the next governor, whoever that might be.

Who would be likely to get such a plum? Would it be one of those senators-in-waiting who had hoped Feinstein would retire? Could it be Gov. Jerry Brown, who could finally take his act to Washington after losing three bids for the White House and one for the Senate himself?

Or could it be the next governor, making a deal with the lieutenant governor to shift to the Senate and thus allowing No. 2 to move up to No. 1? Maybe we should be paying more attention to who’s running for lieutenant governor next year than the office normally deserves.

Those gears are gnashing.

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Dan Walters has been a journalist for more than 60 years, spending all but a few of those years working for California newspapers. He began his professional career in 1960, at age 16, at the Humboldt Times...