By Luc Cohen

NEW YORK (Reuters) - Philadelphia Mayor Jim Kenney stands poised to score a victory that has eluded more than 40 U.S. public officials who took on the powerful U.S. soda industry, if the city council votes on Thursday as expected to slap a tax on sweetened drinks.

After a bitter, months-long battle, the city council will vote on a proposed 1.5 cent-per-ounce tax on sugary and diet drinks. The council already approved the plan in a preliminary vote last week, and the votes are not expected to change.

The City of Brotherly Love would be the biggest U.S. city to have such a tax. The much smaller Berkeley, California, is the only other.

Similar efforts, including several spearheaded by former New York City Mayor Michael Bloomberg, were defeated after intense lobbying from organizations like the American Beverage Association, which opposes the Philadelphia move and represents Coca-Cola Co and PepsiCo Inc.

The Philadelphia tax would mark a major victory for health advocates who say sugary drinks cause obesity and diabetes. But experts noted that those concerns were not the focus for Kenney and other backers of the tax as they took on critics complaining that "nanny state" public health measures intrude into residents' personal lives.

Instead, Kenney rewrote the soda-tax advocate's playbook. He played up the benefits of the cash injection from the tax into the city's depleted coffers. In the first year, the tax is projected to raise $91 million, and he pledged to spend funds on public programs such as universal pre-kindergarten.

The strategic shift could lend momentum to movements in San Francisco, neighboring Oakland, California and Boulder, Colorado. Residents of those cities will vote in November on similar taxes, which could deal further blows to a U.S. soft drink industry already beleaguered by declining soda consumption.

With Americans growing wary of sugary products, U.S. soda consumption fell for the 11th straight year in 2015, according to Euromonitor data.

AVOIDING THE BLOOMBERG TRAP

Bloomberg made public health a centerpiece of his tenure as New York City mayor between 2002 and 2013. He moved to limit smoking in parks and restaurants, ban transfats, and require calorie counts posted in some restaurants.

On soda, he pushed for a tax, then a ban on soda purchases with food stamps, and finally a much-lampooned limit on the size of sugary drinks. These efforts were ultimately struck down, with critics decrying the moves toward a "nanny state."

The strategy worked in Britain, where a new soft drinks levy was announced in March after officials emphasized the country's obesity crisis, saying it cost the economy billions of pounds a year and was a huge burden on the state-funded health system.

The approach never worked in Philadelphia. Michael Nutter, the previous mayor, twice tried to pass a soda tax as a health initiative and a way to plug a budget shortfall. He was unable to push it through city council.

Kenney, who became Philadelphia mayor in January, had made a campaign pledge to provide universal pre-kindergarten, and he kept that issue as his focus. A spokeswoman said complex state laws on taxation made enacting a citywide soda tax the best option to raise revenue for that signature proposal.

"I was a relatively small player in the debate here," said Thomas Farley, who became the city's health commissioner in February after working for the Bloomberg administration in a similar role.

"This was the mayor's plan, not my plan, (but) I absolutely embraced it."

Bloomberg personally contributed funding to support Philadelphia's pro-tax campaigners.

FIZZING WESTWARD

Opponents of Philadelphia's soda tax argued that the measure will disproportionately hurt the poor and prompt Philadelphians to travel to nearby suburbs to buy soda.

Out west, Boulder hopes to use revenue from a soda tax on health programs, and San Francisco and Oakland officials would recommend but not require the funds raised to go toward obesity and diabetes prevention.

When Berkeley passed its soda tax in 2014, industry groups dismissed the measure as a fluke given the city's largely white population and reputation as a hotbed for liberal measures.

But Philadelphia is the fifth largest U.S. city with 1.6 million people. "No one can trivialize it as they can trivialize Berkeley," said Larry Tramutola, a California political strategist who worked on the Berkeley campaign and is currently leading the San Francisco and Oakland efforts.

(Additional reporting by Melissa Fares in New York; editing by Josephine Mason and David Gregorio)