“People want some basic rights,” said Alastair Mactaggart, the 51-year-old real estate developer who has put more than $2 million of his own money to get the measure off the ground. “People are resentful but accepting because there isn’t any sense of control about their data.”

The California measure has three major components: It gives consumers the right to ask companies to disclose what data they have collected on them; the right to demand that they not sell the data or share with third parties for business purposes; and the right to sue or fine companies that violate the law.

Google, Facebook, major telecommunications companies and California’s Chamber of Commerce have already come out against the initiative, saying it is flawed and a threat to the economic model supporting the internet. They’ve created an organization to fight the measure with a decidedly populist name, “The Committee to Protect California Jobs.”

Political consultants have told the initiative’s backers that they should prepare for the opposition campaign to spend $100 million. Steve Maviglio, a spokesman for the opposition, declined to put a number on the campaign spending, but acknowledged that there is a lot at stake. “It’s California,” he said. “It’s expensive.”

California’s privacy initiative hasn’t been certified yet by state officials for the November election, but it is expected to appear on the ballot. The measure’s backers said they have submitted over 600,000 signatures, far eclipsing the 366,000 minimum requirement.