There seems to be some truth in the old saying that the third time’s the charm, at least when it comes to Philadelphia’s passage of a soda tax. After two previous attempts failed, on 16 June Philadelphia’s city council voted to pass a tax of 1.5 cents per ounce on both regular and diet soda beverages.

Soda sales and their impact on the epidemic of obesity are a hot topic across the US, and much of the world. Philadelphia is the fifth-largest city in the US and the largest to successfully pass such a proposal. Only tiny, liberal bastion Berkeley, California, had passed a plan until last week. Since 2008, some 43 other taxes have been proposed in cities and municipalities and all have failed, faced down by the powerful drinks’ lobby.

Soda sales are declining – in the US they soon look set to be outstripped by sales of bottled water. But still 17% of Americans drink soda at least once every day, according to the Centers for Disease Control and Prevention. And consumption is higher among black and Hispanic Americans and in southern states, where obesity is also above average.

Experts see Philadelphia’s success, and the innovative strategy it adopted to get there, as a sign that other cities will soon follow. “This is an important harbinger of what is going to come and people in Philadelphia will see this as important part of their history,” predicted Kelly Brownell, dean of the Sanford School of Public Policy at Duke University, who is an advocate of the soda tax.

Historically, the idea for a soda tax first came up in the context of improving health, Brownell said. But initiatives that focused on the tax as a means to cut consumption for health reasons have met with derision and failed. Americans don’t like being told what to do and the soda lobby has used that to its advantage.

Recasting the tax as a budget issue, as Philadelphia’s mayor Jim Kenney did, has proved more palatable. The tax, which is projected to bring in $91m in the first year, will be used to pay for expanding pre-K as well as improving parks, libraries and recreation centers. Philadelphia has high fixed costs which made it difficult to find revenue to pay for expanding pre-K in the city, explains Lauren Hitt, spokeswoman for Kenney. The mayor did not want to raise property taxes again, said Hitt, so the soda tax was settled on as an alternative revenue source to help fund pre-K expansion.

David Goldberg, spokesman for Healthy Food America, an advocacy group that supports soda tax initiatives, predicts that San Francisco, Oakland and Albany, California as well as Boulder, Colorado, will all pass similar taxes this year in the wake of Philadelphia’s success. A number of other cities are now in the primary stages of considering the tax as well, he adds.

The American Beverage Association (ABA), the lobbying group for soda manufacturers, which strongly opposes the tax, has said it will “take legal action to stop it”, according to spokeswoman Lauren Kane. The ABA has referred to the tax as “regressive” and “discriminatory”, noting that “similar tax proposals have been rejected 43 times across the country in the past eight years, including twice in Philadelphia”. A tax can be regressive if a larger percentage of a poor person’s income goes into acquiring an item, or a lower income bracket is taxed at a higher rate than a higher income bracket.

Philadelphia feels confident about its legal standing, said Hitt, noting that the city’s lawyers vetted the proposal and addressed all the arguments that the ABA has raised. The US has many regressive taxes, and being regressive alone does not make a tax impermissible, explained Mark Luscombe, principal federal tax analyst at Wolters Kluwer Tax and Accounting, citing examples of other regressive taxes such as tobacco and alcohol taxes which impact the poor disproportionately more than the better off.

Goldberg argues that it makes sense that a tax that impacts poorer communities, would also be the one that benefits those communities by expanding early education for children. It was a smart policy decision by Philadelphia’s mayor to “carve out some of the industry profits that have come out of poor communities primarily and put them back into the community to benefit the future prospect of kids in those poorer communities”, Goldberg said.

Other legal arguments raised include those around Pennsylvania’s constitution, which has a uniformity clause. The uniformity clause means all items in a certain class must be taxed at the same rate, so for example all real estate, whether it is residential, commercial, or industrial is taxed at the same rate. So if a tax is imposed, all beverages, including bottled water, could be seen as one class. Sweetened beverages, Hitt argues, are a distinct class because of their negative health effects.

The case could “for sure” go to court and may take a couple of years to resolve, said Richard Briffault, a professor of legislation at Columbia Law School. In the meantime, the ABA would seek a stay pending litigation, which it may or may not be granted, explains Briffault.

Berkeley passed its soda tax in 2014. Soda consumption in Berkeley was already low before the tax. The ABA did not challenge Berkeley’s soda tax, underscoring the impact Philadelphia’s tax is expected to have on similar measures in other cities. “If the Philly tax didn’t mean anything, the soda industry would not have plunked more than $4m into fighting it and promised more in implied bribes,” says Marion Nestle, professor of nutrition and food studies at New York University.

While Philadelphia works to implement its tax, which is slated to go into effect in January 2017, other cities are taking note of its successful strategy. “There is great public support for tax funds earmarked for social purposes,” says Nestle. Focusing on soda taxes as a revenue source also brings “a whole other group of political figures to the mix”, points out Brownell. Previously, only politicians focused on health would get involved with soda tax proposals, but the new strategy brings in politicians who are looking for new revenue generating possibilities for projects for their constituents, explains Brownell. “My guess is that the floodgates will open pretty quickly, Brownell says.