An employee at a store arranges Coca-Cola sodas in Alexandria, Virginia. Reuters

Two California cities could make history Tuesday if residents vote to impose a tax on sugary drinks. A “yes” vote in either San Francisco or Berkeley would be a first in the nation and may trigger a ripple effect in other areas, potentially accelerating the gradual decline of American soda consumption. The measures face strong opposition from the beverage industry, which has poured tens of millions of dollars into defeating similar proposals in more than two dozen American cities and states over the past five years.

In Berkeley, a city of 100,000, passage of the soda tax proposal requires a tally of just more than half of voters in favor. It would add a penny per ounce on drinks with caloric sweeteners, such as sodas, energy drinks, coffee syrups and even some juices. San Francisco’s tax would add two cents per ounce and requires a two-thirds majority to pass in the city of 837,000.

The fight over sugary drinks isn’t limited to Berkeley and San Francisco -- two renown centers of progressive, often radical, thought. The tax proposals reflect a broader shift in American taste away from foods and drinks that are perceived less wholesome and toward choices that appear to be healthier.

“People are getting really tired of the messaging they’re getting from the beverage industry,” said Maureen Erwin, spokesperson for Choose Health SF, a campaign supporting the soda tax. “People are -- more and more -- understanding the linkage between sugar-sweetened beverages and diseases like diabetes.”

Choose Health SF has received endorsements from dozens of community groups, ranging from nursing and dental associations to elementary schools and even local newspapers like the San Francisco Chronicle. The Berkeley vs. Big Soda campaign has also secured endorsements from several community and health groups like the American Heart Association as well as more than $600,000 from Michael Bloomberg, former mayor of New York who tried to ban supersize soft drinks there in 2012.

And while Berkeley’s “yes” campaign has collected less than $1 million, and San Francisco’s only about $275,000, the American Beverage Industry has spent $9.1 million in San Francisco and more than $2 million in neighboring Berkeley on “no” campaigns. The industry group, funded by Coca-Cola Co., PepsiCo Inc. and Dr. Pepper Snapple Group Inc., argues in radio and TV ads that taxes are already high for residents and that soda is being unfairly targeted.

“At a time when people in the Bay Area are confronting an affordability gap, the last thing we need is a new beverage tax,” Roger Salazar, spokesperson for the American Beverage Industry, told CBS San Francisco. “We don’t disagree that there are things we need to do in public and society to improve our diet and nutrition, but a regressive tax -- a misguided tax -- that does nothing to really improve people’s health and does everything to increase the economic burden on them is not the right way to go about it.”

The industry is also broadcasting its removal of full-calorie sodas from schools and its pledge to cut beverage calories consumed per person by 20 percent by 2025, “the single largest effort by an industry to help fight obesity,” the group says.

San Francisco’s office of the controller estimates the proposed soda tax would raise prices by 23 to 36 percent and generate $35 million to $54 million in tax revenue annually. The money would go to school nutrition, public education and fitness programs. Supporters of the tax cite research concluding that a 2-cent tax could reduce soda consumption by as much as 10 percent. Tax revenue from Berkeley’s soda tax would go toward the city’s general fund.