Washington (CNN) In her 25 years on Capitol Hill, California Sen. Dianne Feinstein has never been one to shy away from vocalizing her views.

However, some of her recent comments -- including Tuesday when she suggested the Deferred Action for Childhood Arrivals program, is on shaky legal ground -- have caused backlash among liberals in the Golden State and prompted discussion about whether she should seek a fifth term. DACA is shorthand for the program started by President Barack Obama to give temporary legal status to certain children of undocumented immigrants. President Donald Trump on Tuesday gave Congress a six-month ultimatum to either pass a permanent version or put that legal status in jeopardy.

California, which has the largest DACA population by far, would be affected more than any other state, so Feinstein's admission that the program could be legally tenuous set off alarm bells on social media among her constituents.

Feinstein, a top Democrat and, by a few months, the oldest sitting senator, is nearing the end of her term and has not formally declared her intention to run for re-election in 2018. She hasn't ruled it out, either.

Some of her critics in the fiercely blue state believe Feinstein is not speaking out strongly enough against President Donald Trump, which has led to plenty of talk about whether she will face a major primary calendar. (Note: California has open primaries and the top two finishers, regardless of party affiliation, square off on Election Day, which has increasingly led to Democrat vs. Democrat showdowns in November).

Many California political experts say even with recent resistance toward Feinstein, she wouldn't face much competition should she decide to run again.

"She's well known, well funded and well organized," Sherry Bebitch Jeffe, a University of Southern California professor, told CNN. "She's a very popular politician, it would be difficult for anybody else but Dianne Feinstein to win, assuming the election were today or tomorrow."

Others say her recent centrist comments could be problematic.

"Senator Feinstein has been a very effective senator for a long time and she will be a heavy favorite if she does run for re-election," Brian Fallon, a CNN political commentator and former press secretary for Hillary Clinton's 2016 presidential campaign, told CNN. "But her impulse to give Donald Trump the benefit of the doubt when he does not deserve it only fuels her critics."

'Out of fashion'

The sentiment that Feinstein shouldn't run again began publicly formulating as early as January, when crowds protested outside her Los Angeles office and her San Francisco mansion.

"Primary Feinstein if she's not more aggressive!" read a sign during the protest, where people chanted" "Hey, Feinstein! Hear us shout, if you don't, we'll vote you out."

Jeffe said she noticed the recent uptick in Feinstein resistance while at her April town hall in Los Angeles.

"The progressive, very liberal, very activist portion of the Democrat Party base were really loud," Jeffe said. "I watched Sen. Feinstein's face; she really didn't expect that kind of blow back."

Meanwhile, Jeffe described California Sen. Kamala Harris' L.A. town hall -- which she also attended -- as a "love fest."

Dan Schnur, director of the Jesse M. Unruh Institute of Politics at the University of Southern California, said Feinstein's brand is more "old fashioned," especially when compared to Harris, who is seen as a rising star in the party and a 2020 presidential prospect.

Feinstein ran for mayor of San Francisco in the 1970s and later served in that position after Mayor George Moscone was assassinated.

Feinstein's "brand of centrism is decidedly out of fashion in both parties," Schnur told CNN. "It's not surprising that some of the most progressive voices in the party here [in California] are upset with her."

California has changed a lot in the 24 years Feinstein has been in the Senate. For starters, Hispanics made up about a quarter of the state population in 1990. But during her time in office they became the largest ethnic group, surpassing whites and helping to make the state a majority minority population. The politics of the state have also changed. California may have given the country two Republican Presidents, but it hasn't voted for a Republican for President since 1988. And opposition to Trump in the state is fierce.

RELATED: The California GOP's last gasp



Last week during an appearance at the Commonwealth Club of California in San Francisco, Feinstein generated more outrage after Last week during an appearance at the Commonwealth Club of California in San Francisco, Feinstein generated more outrage after encouraging people to "have some patience" regarding President Donald Trump.

"I think we have to have some patience, I do," Feinstein said. "It's eight months into the tenure of the presidency. ... We'll have to see if he can forget himself and his feelings about himself enough to be able to have the empathy and direction that this country needs."

The San Francisco Chronicle reported the crowd -- which gave Feinstein a standing ovation at the start of the event -- "reacted with stunned silence, broken only with scattered 'No's' and a few hisses and some nervous laughter."

Among those who were upset: California State Senate leader Kevin de León, who is a rumored future candidate for governor or US Senate.

"We don't have much patience for Donald Trump here in California," he said in a statement . "This president has not shown any capacity to learn and proven he is not fit for office. It is the responsibility of Congress to hold him accountable — especially Democrats — not be complicit in his reckless behavior."

He also countered Feinstein's comments -- without mentioning her name -- about DACA during in an interview with CNN's Erin Burnett on Tuesday.

"Over 100 legal scholars already opined that in fact DACA is constitutional," he said.

JUST WATCHED Kevin de Leon asserts DACA is constitutional Replay More Videos ... MUST WATCH Kevin de Leon asserts DACA is constitutional 00:32

Ashley Schapitl, a spokesperson for Feinstein, clarified Feinstein's comments in a statement to CNN earlier this week.

"Sen. Feinstein is a staunch champion of DACA and signed onto an amicus arguing its legality," Schapitl said in a statement to CNN earlier this week. "It's no secret the 5th Circuit may hear a lawsuit brought by Republican attorneys general. That's obviously the legal threat to which she was referring. She'll continue to speak out in favor of DACA and the DREAM Act."

De León's political director Courtni Pugh has shut down 2018 talk.

"Senator de León has his head down and is focused on California's Legislative business," she told POLITICO

Meanwhile, Los Angeles Mayor Eric Garcetti, Secretary of State Alex Padilla, Rep. Adam Schiff and Rep. Eric Swalwell have all been mentioned as other potential candidates for Senate, should Feinstein not run.

'Not a problem'

Feinstein's office did not respond to CNN's requests for comment on this story.

However, in a recent interview with Mother Jones , Feinstein said this of recent protests surrounding her: "These are very small demonstrations. I've lived through big riots. I've lived through the torching of 12 squad cars. I've lived through assassinations. These have been very polite and not a problem."

After backlash from the San Francisco event, Feinstein issued a statement emphasizing she has stood up against many of the controversial things Trump has said and done.

"During this tumultuous time, I'm working to protect the progress we've made and find a way to get things done for Californians during a period of total Republican control of Washington. I've been strongly critical of President Trump when I disagree on policy and with his behavior," she said. "Most recently, I was appalled by his comments in response to Charlottesville and the pardon of Sheriff Joe Arpaio. President Trump said that there were 'very fine people' in a crowd chanting 'Jews will not replace us.' There's nothing 'fine' about white supremacists, Nazis or the KKK."

She is also the top Democrat on the judiciary committee, which is investigating the Trump campaign's alleged collusion with Russians during the 2016 presidential race.

"A party icon"

Feinstein has remained adamant about working with both sides of the aisle.

"I truly believe that there is a center in the political spectrum that is the best place to run something when you have a very diverse community. America is diverse; we are not all one people," she told CNN's Dana Bash in an interview for CNN's "Badass Women of Washington" series. "We are many different colors, religions, backgrounds, education levels, all of it."

JUST WATCHED The assassination that shaped Dianne Feinstein Replay More Videos ... MUST WATCH The assassination that shaped Dianne Feinstein 07:04

That philosophy has kept her popular, for the most part, both in California and among her peers on the Hill.

In a March survey, the Public Policy Institute of California found 49% of California adults approve of Feinstein.

"The former San Francisco mayor is an important, effective player in Congress with lots of achievements," he wrote. "For no other reason than maintaining her ability to deliver for California, she's wise not to hammer Trump just for the sake of hammering him and making leftists cheer."

Schnur agrees Feinstein's brand remains strong even if recent backlash suggests otherwise.

"Her relationships and support are far too strong to cause her any serious challenge in a re-election campaign," he said. "Any rising Democrat party leader who might want to run for that senate seat is probably smart enough not to risk the backlash that would come with running against a party icon."