Riverside, California (CNN) As she has trudged toward the Democratic nomination, Hillary Clinton has struggled to find a message that could impassion her Democratic voters the way her rival Bernie Sanders has.

But that changed this week in California when she turned her full attention to Donald Trump . With the brash real estate magnate as her full-time foil, Clinton finally seemed to find her voice.

In speech after speech across the Golden State, Clinton delivered a fiery, point-by-point takedown of the real estate magnate, casting him as a greedy bully who was eager to profit from the financial woes of the middle class Americans who lost homes and jobs in the 2008 economic crash.

"I will continue to stand up and speak out against what he says -- the kinds of positions and policies he's putting forward, the way he treats people, how divisive he is," Clinton said Wednesday in Buena Park.

It could be a key turning point for her campaign. Her supporters and donors have been baffled for months about her inability to vanquish Sanders, given her influence and the depths of her support in the Democratic Party. Recent polls have shown Trump closing in on Clinton in potential general election matchups -- raising the level of alarm about her ability to focus on the general election campaign.

But while Clinton may have momentarily found her stride, fresh controversies like the one that emerged Wednesday -- the State Department Inspector General report saying she failed to follow the rules or inform key department staff regarding her use of a private email server -- could quickly knock her back off message.

JUST WATCHED State Dept. IG: No one okayed Clinton private email server Replay More Videos ... MUST WATCH State Dept. IG: No one okayed Clinton private email server 05:33

Though the former secretary of state has not yet clinched the magic number of delegates needed to win the Democratic nomination, she campaigned here as though Sanders' campaign was the farthest thing from her mind.

Her singular focus on Trump was most striking when she campaigned a few miles from Sanders in Riverside Tuesday, but never mentioned him. Delivering a speech that sent a jolt of electricity through the initially subdued crowd, she vowed not to let Trump go unanswered.

Targeting Trump's image as a champion for the little guy as a fraud, Clinton pounded Trump repeatedly for comments that he made in 2006 in a Trump University audiobook where he said he "sort of" hoped that predictions of looming housing market crash were accurate. If the bubble burst, "you can make a lot of money," he said.

"Why on earth would we elect somebody president who actually rooted for the collapse of the market?" she said with indignation in Riverside as the crowd roared their approval and chanted her name. "The fact is Donald Trump thought he could make money off of people's misery."

In Orange County on Wednesday, Clinton also cast Trump as "a divider" who has denigrated women, Muslims and people with disabilities. Keying off his raucous event in New Mexico on Tuesday night, she specifically called him out for attacking Gov. Susana Martinez.

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"He makes a habit of insulting women," Clinton said in Buena Park. "Last night he insulted the Republican Governor Martinez of New Mexico -- just gratuitously. I don't know. He seems to have something about women."

"Whatever reason he does it, it is setting Americans against Americans," she said. "It is a recipe for more divisiveness at a time where we must be united."

Trump did not directly respond to those attacks in Anaheim Wednesday, but told the crowd he was eager to run against the former secretary of state -- who he continues to call " Crooked Hillary ."

Recalling her 2008 campaign ad, where she was portrayed as the only candidate qualified to take the 3:00 am emergency call in the White House, Trump repeatedly questioned her judgment and fitness to be commander-in-chief, faulting her for turmoil in Iraq and Libya.

"You remember the famous ad -- when they call at 3 in the morning, who's going to be there to answer the call?" Trump said. "She was sleeping. They called. They kept calling. Did you see hundreds and hundreds of emails and calls? And they kept calling and she was sleeping, folks. She was sleeping. I don't sleep much. I don't sleep much."

JUST WATCHED Trump: Hillary Clinton a 'lowlife' Replay More Videos ... MUST WATCH Trump: Hillary Clinton a 'lowlife' 00:55

After watching Trump slay one Republican rival after another, Clinton's campaign has spent months workshopping the most effective way to target the real estate mogul.

For now, they seem to have settled on that three-prong attack -- that Trump is a businessman who only protects his own interests; that he is a man who is incapable of working with others; and a candidate who would pose a risk to national security.

Attempting to tie those threads together at an International Brotherhood of Electrical Workers event on Tuesday, Clinton suggested that Trump may have never paid any federal income tax. Trump has declined to release his tax returns, because he says he is under audit.

"He goes around saying, 'Well we have got to have a stronger military,'" Clinton said. "Well he certainly doesn't want to pay a penny to protect our men and women in uniform."

JUST WATCHED Elizabeth Warren calls Trump 'insecure money-grubber' Replay More Videos ... MUST WATCH Elizabeth Warren calls Trump 'insecure money-grubber' 01:06

Top campaign aides, in discussions with Clinton, have settled on a strategy of responding to Trump with policy-focused attacks while casting him as someone who has no idea what real Americans actually want.

Clinton will not, aides say, respond to Trump's personal attacks, particularly about her husband's marital indiscretions.

I fight for working families every day, @realDonaldTrump. You fight only for Donald Trump. — Elizabeth Warren (@elizabethforma) May 25, 2016

Clinton's surrogates have gotten behind that message, taking on Trump's business dealings and painting him as a selfish and callous self-promoter. On Wednesday, Massachusetts Sen. Elizabeth Warren leveled a series of Twitter attacks on Trump, but one stuck out to Clinton's aides.

"I fight for working families every day, @realDonaldTrump," Warren tweeted . "You fight only for Donald Trump."

Sanders: It's not over

As the contours of the potential Trump-Clinton matchup take shape, Sanders is making his last stand here in California before voters cast ballots on June 7, which will mark the end of the primary season.

Though they acknowledge that Sanders' path to victory is a narrow one, the young, diverse, passionate supporters flocking to his events have a very clear message for Clinton: It's not over.

"When there are large voter turnouts we win," Sanders said at his Riverside event this week. "We are going to be running up and down this beautiful state. We are going to be speaking to over 200,000 Californians ... We are going to win here in California."

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He asked the largest state in the nation to tell "the entire world" that "California believes in the political revolution."

Most striking at Sanders' events, however, is how much work Clinton may have ahead of her to win over his followers -- and how much frustration they feel at what they see as condescension from her campaign.

That was emblematic in a T-shirt that some Clinton backers were wearing this week as the Democratic candidates campaigned across town from one another. "Spoiler Alert," the shirt said. "Clinton wins."

"She's not a trustworthy person to vote for," said Yasmeen Dabbos, a 20-year-old second-year anthropology student at UC Riverside as she waited to enter Sanders' event. "I didn't like her from the beginning and I feel like people wanted her there just because they thought she was the only option. But I always felt like there was someone else who could beat her, and Bernie obviously filled that position."

While Dabbos plans to volunteer for Sanders, she said would never put in that kind of effort for Clinton.

"I would just cast my ballot, that's all I could do for her," Dabbos said. Even then, she added, it would be more of a vote against Trump.

President Barack Obama, himself familiar with a long, drawn-out primary, called it "a grind" when asked about it during a news conference in Japan Thursday.

"I guarantee you the eventual nominee sure wishes it was over now, because this is a grind," he said. "It's hard. And in some ways, one of the things I've always found is that it's a lot more draining arguing against your friends than it is arguing against your political opponents. It weighs on you more. Being criticized by folks in your own party always hurts just a little bit more."