So what happened? And what's next for the food movement?
County-by-county election results for Prop. 37 showed that the measure enjoyed strong support along California's liberal coast. Santa Cruz County was the measure's biggest bastion of support, with 65.6 percent supporting, followed by Humboldt County with 65.2 percent.
But the measure lost in nearly all of the inland counties, including the state's agricultural center of Fresno, Kern, Kings and Tulare counties. In Fresno County, 63.6 percent voted no while 36.4 percent voted yes. The measure won in farm-heavy Imperial County and the Sierra Nevada mountain counties of Mono and Alpine.
"This is a story about money," said Stacy Malkan, media director of the Prop. 37 campaign, on Wednesday. "Our loss had to do with being outspent. We didn't have the funds to compete on the air in the central regions of the states."
Supporters of Prop. 37 said Wednesday that efforts to require labels of genetically modified foods now shift to other states. Signature gathering is underway for a similar ballot initiative in Washington State in November 2013, along with legislative efforts to require labeling in Connecticut and Vermont.
Many said the high-profile campaign in California raised national awareness of GMOs, and a petition
In a post-election conference call with journalists Wednesday, the Yes on Proposition 37/California Right to Know campaign said the election results, while disappointing, were not surprising given the $46 million raised by the No side.
St. Louis-based Monsanto, a leading maker of genetically engineered seeds, was the largest single contributor with $8.1 million. The Yes side raised $9.2 million, with the largest contribution coming from Joseph Mercola, a popular holistic health activist from Illinois.
"We fought Monsanto and Dupont to a standstill last night," said Dave Murphy, executive director of Food Democracy Now. "More than 4 million Californians are on record saying they want to know what's in their food. This is a dynamic moment for the food movement."
Pamm Larry, a former farmer and midwife from Chico, is credited with launching the grass-roots effort to label GMOs in California in January 2011. She helped lead nearly 10,000 volunteers across the state. But the campaign had little in the way of an organized ground game and only seven or eight paid field organizers.
"We were very strong in the northern part of the state," said Larry. "We had people in Humboldt, but we didn't have as many people in Modesto and Stockton."