Hillary Clinton's campaign had once hoped the California primary could be a coronation for the former secretary of State, the last major stop en route to claiming the Democratic presidential nomination.
Instead, it has turned into a dogfight with Bernie Sanders, who has been campaigning nonstop through the state. With at least one public poll showing the race now a tie, the Clinton campaign has decided to step up her appearances in the state.
"It's going to be closer than we thought," said former Los Angeles Mayor Antonio Villaraigosa, a longtime Clinton backer, adding that he ultimately expected her to win the state.
"Hillary's going to be the nominee, but California's the big prize, and obviously she'd like to go into the convention with a win in California," he said.
Clinton does not need to win California to clinch the nomination. She now has 2,310 delegates to this summer's nominating convention, according to the latest count, and needs only 73 more for a majority. She is expected to win a significant majority of Puerto Rico's 67 delegates in its primary on Sunday.
By the time California and five other states vote on June 7, Clinton will need only a few of the 694 pledged delegates up for grabs that day.
Despite all that, a loss in this enormous, diverse, overwhelmingly Democratic state would be an ugly stain in the lead-up to the party's convention in July in Philadelphia.
"She's going to be able to give an important victory speech on Tuesday as the presumptive nominee, and it's clearly more appealing to do that when the chyron at the bottom of the [television] screen is reading that Clinton is the projected winner of California," said Dan Newman, a veteran Democratic operative whose San Francisco-based firm is aiding Clinton's campaign in the state.
"California is important because it's California. It's big, it's overwhelmingly Democratic, and she's the nominee regardless, but it would send her into the general election with an extra head of steam to win California. It's certainly not do or die, but it's always preferable to win everywhere."
And Clinton, despite her significant lead over Sanders in the popular vote and in the delegate tally, has not won everywhere. The Vermont senator has racked up 20 wins, compared with her 26, and he has taken three of the last five contests.
Clinton was widely expected to win California this year by about 8 percentage points, the same margin by which she beat then-Sen. Barack Obama in the 2008 primary. She and her husband, former President Bill Clinton, have forged strong ties to the state's Democrats during their decades in public life.
"California has been uncommonly good to my family," Bill Clinton told more than 1,000 people in a courtyard at Los Angeles Trade-Technical College in April when he campaigned for his wife here.
The state, where the couple first lived together as boyfriend and girlfriend in the early 1970s, has provided support, solace and tens of millions of dollars in campaign cash for the family's pursuits.
Bill Clinton clinched his 1992 Democratic nomination in California, over now-Gov. Jerry Brown. Hillary Clinton's victory here in 2008 provided momentum she sorely needed that allowed her to continue her ultimately unsuccessful bid.
But Sanders has not let up here, holding rallies that draw thousands of ardent supporters as he barnstormed California in recent days.
"California is the big enchilada, so to speak," Sanders said on NBC's "Meet the Press" on Sunday. "Obviously, if we don't do well in California, it will make our path much, much harder. No question about it.'
Sanders' aggressive approach to campaigning in the state has clearly helped him, said veteran Democratic operative Garry South, who is not working for either campaign.
"He's campaigning in California like he was running in Iowa," South said. Most presidential candidates "fly in, do a rally and go to Beverly Hills to do a fundraiser, and then they leave."
Clinton's campaign and her supporters have responded. The candidate purchased at least $1 million of ad time last week, reversing a pattern of not spending money on ads in the final primaries.
Her allies have also announced plans to advertise to support her bid, albeit on a relatively small scale. The American Federation of Teachers was the latest backer to announce such a plan Monday.
And Clinton's campaign announced Monday that she plans to return to the state on Thursday, earlier than expected, and will campaign here through the eve of the primary.
A spokesman for Clinton's campaign said her efforts are aimed at showing as much support as possible from Democratic voters.
"Hillary Clinton has fought for every vote since the start of the primaries, and she's going to continue that until the end, no matter how far ahead we are in delegates," Jesse Ferguson said.
"Our grass-roots campaign is built on ambitious organizing efforts especially in California's diverse communities and fueled by her commitment to meet directly with as many voters as possible."
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