"If I win, believe me, we're going to start opening up the water so that you can have your farmers survive, so that your job market will get better," Trump told a few thousand cheering supporters at a sports arena in Fresno.
After a private half-hour meeting with farmers, Trump said the group told him there was no drought in California, but rather a failure to preserve and wisely use the water the state has on tap.
"You have a water problem that is so insane," he said. "It is so ridiculous, where they're taking the water and shoving it out to sea."
He mocked environmentalists for "trying to protect a certain kind of 3-inch fish," repeating an apparent reference to the delta smelt, a fish on the verge of extinction that is regarded by scientists as a barometer of California's environmental health.
Trump's remarks at an exuberant rally in the state's agricultural heartland came a day after he delivered an ardently pro-drilling speech at a petroleum conference in North Dakota.
It also marked a day when — for a few hours at least — California enjoyed a flurry of candidate activity more typically seen in such early-voting states as Iowa and New Hampshire.
While Trump staged rallies in Fresno and San Diego, the presumptive Democratic nominee,
For more than a century, competition over California's often scarce water supply has pitted a wide array of powerful forces against one another — big cities, the agriculture industry and conservationists among them.
As with many of Trump's promises, such as forcing Mexico to pay for a border wall, or reversing years of job losses in the U.S. manufacturing industry, he offered no specifics for how he would achieve these policy goals. Rolling back environmental protections would require changes in both state and federal environmental regulations, which enjoy strong backing among California voters and many lawmakers.
Lester Snow, executive director of the California Water Foundation, a nonprofit group that supports research and other projects, said Trump's comments mischaracterize and oversimplify the situation.
"Playing off 'farmers versus fish' is a sound bite but isn't a solution to any real-world problems," he said. "It's just an old, tired bumper-sticker way of talking about California's water problems."
He took issue with Trump's claim that "they're taking the water and shoving it out to sea."
"It's not a waste of water," Snow said, noting freshwater runoff to the Pacific Ocean helps prevent saltwater intrusion, which could contaminate groundwater supplies.
Much of Trump's hourlong speech consisted of stock lines, though he made a boastful vow to put heavily Democratic California in play in November.
"If I don't win, they are gonna spend one hell of a fortune fighting me off," he said.
He bashed Clinton for using a private email server as secretary of State and recalled the Whitewater real estate scandal dating from her husband's years as Arkansas governor. "She's always skirted the edge," Trump said.
He drew laughter and tears as he continued mocking Clinton as "screaming into the microphone all the time."
"Actually, that's why I turned it off last night," he said of a Clinton television appearance. "It wasn't that she was lying about me in every single corner. I just couldn't stand it."
Noting his strong support among male voters and his unpopularity among women, Trump said: "I love women. Believe me, I love women. I loooove women. And you know what else? I have great respect for women. Believe me."
His Fresno appearance drew about 200 peaceful demonstrators. In San Diego, several hundred protesters gathered in the downtown Gaslamp District, their access to the convention center blocked by dozens of police officers.
Janitors from a local union waved mops, mothers pushed strollers and Latino activists blasted Trump with pinata effigies and Spanish-language chants.
"El pueblo unido, jamas sera vencido!" ("The people united, will never be defeated!") they yelled.
"Speak English," some Trump supporters hollered back.
Inside, Trump nodded to the region's large military presence, inviting veterans to join him on stage. A crowd of thousands sprawled across the vast convention floor cheered wildly as he denounced illegal immigration and trade deficits with China, Mexico and Japan.
He also rambled at length about his upcoming civil fraud trial in San Diego federal court over his defunct Trump University. Students allege they wasted their savings on worthless real estate courses.
Trump blasted the judge overseeing the case, Gonzalo Curiel, drawing loud boos when he mentioned he was appointed to the bench by President Obama.
"The judge, who happens to be, we believe, Mexican, which is great — I think that's fine. You know what? I think the Mexicans are going to end up loving Donald Trump when I give all these jobs, OK?… I think they're going to love me."
"I'm getting railroaded by the legal system," Trump said. "Frankly, they should be ashamed."
Clinton, by contrast, held a low-key meeting with supporters in Oakland.
Welcoming her to the Home of Chicken and Waffles, a local soul food institution, Mayor Libby Schaaf alluded to Trump's recent description of the city as one of the most dangerous in the world.
"We are incredibly proud to have Secretary Clinton here in Oakland today," Schaaf said. "Despite what some people say about the level of safety in this city, Oakland has made incredible gains.... We have become a tremendously safer city."
The lengthy discussion that followed was more policy-oriented than overtly political — though Clinton implicitly hit on a recurring theme that Trump is a divider rather than uniter.
"I want to be a champion for Oakland and all the Oaklands of America, places that have challenges like any part of our country and any kind of human endeavor, but places that are coming together," Clinton said. "We're stronger together when we work together, when we come up with these approaches and we bring everybody to the table."
Later, Clinton talked about the downsides of gentrification, a growing Bay Area concern post-Great Recession as middle-income and even relatively well-to-do residents are finding themselves priced out of the economically booming region.
"There's advantages, of course, to fixing up neighborhoods and making them attractive and all the rest of it," Clinton said. "But I think it's a big price to pay if we displace everybody who has been there and who has gone through the bad times and deserve to be part of the good times."
Sanders made several stops across Southern California, starting with a morning rally in San Pedro, where he delivered a fiery rebuke of both major political parties.
"It is too late for establishment politics, establishment economics — we need a political revolution," said Sanders, with the towering cranes at the Port of Los Angeles as his backdrop. "We are tired of politicians in both parties hustling money from the wealthy and the powerful."
As he has in recent days, Sanders steered away from criticizing Clinton, apart from a passing reference to her support from a richly funded political action committee. Instead, he focused on the backing Trump has received from Las Vegas gambling magnate
"It's an absurdity when you have a billionaire like Sheldon Adelson contributing large sums of money to another billionaire like Donald Trump," Sanders said. "What a joke … our message is, billionaires are not going to run this country."
"The American people are sick and tired of the status quo," he said, and the crowd outside the Los Angeles Maritime Museum shouted back, "We're not going to take it anymore!"
Later, though, Sanders took direct aim at Clinton in an interview on "The Young Turks," a left-leaning leaning political Web series recorded in Los Angeles.
"Can she lose? Absolutely she can lose," Sanders said of a prospective Trump-Clinton matchup in November. "The reason I'm here, the reason I'm running all over California, is because I think I'm a much stronger candidate."
After Friday, Sanders will have the state to himself for at least the next few days. He plans a weekend excursion through the Central Valley as well as stops in Santa Barbara and Santa Maria.
Clinton's stop was her last scheduled appearance in California after several days of campaigning in the Bay Area and Southern California. She planned a weekend off in New York.
Trump, who has no more California events on his public schedule, was going to head East for a visit Sunday to the Rolling Thunder motorcyclists' rally in Washington and a veterans event Tuesday at Trump Tower in Manhattan.
5:51 p.m.: Updated with additional comments from Bernie Sanders.