Both politicians have been criss-crossing the largest state in the union ahead of Tuesday's primary, and while it is Clinton who is all but certain to prevail in their national battle, Sanders still appears to draw larger and more energized crowds.
The stark difference -- Clinton speaking to hundreds in a high school gymnasium in Oxnard, Sanders inspiring thousands at the Los Angeles Coliseum -- highlights the challenges of a candidate who turns towards her head-to-head battle with Donald Trump with only tepid support from many Democrats.
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"I would say there's some Hillary fatigue out there," Jeremy Jackson, a 39-year-old teacher in Oxnard, told AFP, reflecting on the more than three decades in which Clinton has been in America's public eye.
"Plus, people don't like a common-sense approach. They want extreme."
Clintonites don't have "all the pizzazz, but that doesn't mean we're not as enthusiastic," added a federal law expert in Oxnard who identified herself as Erica B, age 35.
"We're tired of having to defend Hillary, so we're not always super vocal."
Clinton's campaign exudes party establishment -- she was a US senator, served as President Barack Obama's secretary of state, and was first lady in Bill Clinton's presidency, while Sanders epitomizes the scrappy outsider.
She would make history as the country's first female commander in chief, but even that milestone would be tempered after Barack Obama's landmark achievement eight years ago, when he became the first African-American commander in chief.
Clinton's unfavorable ratings are sky high, similar to those of Donald Trump, the braggadocios billionaire who is 2016's presumptive Republican presidential nominee.
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Sanders argued at his Saturday rally that he consistently fares better against Trump than Clinton does.
He also said he will take his fight all the way to the Democratic convention in July where he aims to sway enough super-delegates -- unbound delegates who can vote for whomever they choose at the convention -- in his favor to win the nomination.
It is a tall order. Clinton has amassed 2,313 total delegates, according to CNN's tally, just 70 shy of the number needed to clinch the nomination.
She inched closer to the goal Saturday, winning the caucus in the Virgin Islands, where seven pledged delegates were at stake. Puerto Rico's 60 delegates are up for grabs Sunday.
With more than 600 pledged delegates in play Tuesday, Clinton will wrap up the nominations race June 5 when California, New Jersey and four other states vote.
So why isn't there a swell of support for one of America's most respected women?
Shannon Freshour, a paralegal from Los Angeles who waited in the steamy sunshine to get into Clinton's Oxnard event, offered an answer.
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Clinton is a known quantity for millions, especially those backing her, the 41-year-old said.
"The only enthusiasm that matters is showing up to the polls."
Clinton has won three million more votes in the primary race, Freshour noted. "There is a gap in the idea of what constitutes enthusiasm."
Many Clinton supporters insist she will unite the party and head into the general election with strong advantages over Trump in terms of experience, policy positions, and commitment to improving middle-class and working-class lives.
"I think Hillary's momentum is strong," US congresswoman Julia Brownley said after Clinton's event, noting that the candidate's support has "strengthened" after last week's foreign policy speech in which she hammered Trump.
But Clinton is under threat of losing California, which she won in 2008 when she finished strong against Barack Obama in the primary.
Now she is the one facing an extraordinary push by a challenger.
Sanders backers are firm that if Clinton prevails, she will need to win over skeptical Democrats and independents.
Is Hillary a sure thing for the White House?
"She will have to take into account that what we're following Bernie for is not because he's some sensation, not because he's offering free college to us," 25-year-old Travis Sneider-Eaton, a theater writer wearing a "Feel the Bern" hat, said at the raucous Sanders rally.
"He listens to us."
Others are more forceful, stressing that there is a patina of disingenuousness about the Clintons. But when faced with the prospect of President Trump, they turn pragmatic.
"I have to believe that Hillary is better than Trump, and because of that I'll vote for Hillary" in the general election, said television producer and Sanders supporter Pat McGee.
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