Sen. Dianne Feinstein (D-Calif.) on May 23 on Capitol Hill. (Joshua Roberts/Reuters)

Sen. Dianne Feinstein (D-Calif.) officially declared her intention to run for reelection Monday, ending months of speculation about her future and probably avoiding what would have been an intense scramble of Golden State politics to succeed her.

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

On Sunday, Feinstein hinted in a national television interview that she was likely to run again, telling NBC’s “Meet the Press” that she was close to a formal decision.

Feinstein, 84, is California’s senior senator and the oldest U.S. senator in office. She will be seeking her fifth full term — she won a special election in 1992 to fill out the term of then-Sen. Pete Wilson (R).

In the past week, Feinstein was vaulted once again into the national spotlight as she renewed her campaign to enact gun control legislation in the wake of the deadly shooting rampage in Las Vegas. A fierce advocate for stricter gun laws and restrictions on semiautomatic weapons, Feinstein responded to the Las Vegas shooting — the deadliest mass shooting in recent U.S. history — by calling for a ban on “bump stocks,” devices that allow some semiautomatic weapons to mimic an automatic weapon, which are illegal. The devices were found on several of the weapons in the assailant’s Las Vegas hotel room.

Sen. Dianne Feinstein (D-Calif.) unveiled a bill that would ban "bump stocks," devices that can be purchased online to make legal semiautomatic weapons fire more like automatic guns, on Oct. 4. (Reuters)

Feinstein said her narrowly tailored proposal should be sufficient to earn bipartisan support, but so far, no Republican has signed on as a co-sponsor. Congressional Republicans and President Trump have, however, called for a review of federal policy that currently permits bump stocks.

Feinstein’s decision to run again probably foregoes a costly and potentially chaotic primary campaign to succeed her — although progressive Democrats in California have been clamoring for a primary challenge to her, with some in her party believing she is too moderate or accommodating to Republicans in the age of Trump.

Ahead of her decision, several House Democrats from California, including Reps. Adam B. Schiff, Eric Swalwell and Brad Sherman, were said to be preparing for a Senate campaign if Feinstein opted to retire. Some of the Democrats running for governor, including State Treasurer John Chiang, hadn’t ruled out switching to a Senate campaign. And two prominent Latino Democrats, Secretary of State Alex Padilla and state Sen. Kevin de León, who is term-limited as the Senate president pro tempore, are also known to be angling for higher office.

But California’s most prominent congressional Democrat, House Minority Leader Nancy Pelosi, said Feinstein’s decision was good news for their state.

“For us and the issues in our state, whether it’s our values or needs, it would have been a tremendous loss for Dianne not to run,” Pelosi said in an interview with The Washington Post, noting Feinstein’s senior positions on the Appropriations, Intelligence and Justice committees.

“She’s a tremendous asset to our state. I’m thrilled that she made the decision that she has. It’s a good thing not only for California but our country,” Pelosi added.

Now that Feinstein has announced her intentions, the political future of one other long-serving senator remains unknown. Sen. Orrin G. Hatch (R-Utah), who has served since 1977, has still not officially stated whether he plans to run again. If the 83-year-old opts to retire, Mitt Romney, the 2012 GOP presidential candidate who now lives in Utah, is among those considering a potential campaign.