NEW YORK — Dennis Rivera, a charismatic 53-year-old native of Puerto Rico who has built his health-care workers' union into one of the most potent political forces in the state, is a major reason why even as state tax revenues have gone down, spending on health care has gone up.

Wielding the huge campaign treasury that he gets in $5 monthly increments from about half of his union's 250,000 members, Rivera has made his union a force by going after politicians rather than health-care facilities for money — in fact, by forging unlikely alliances with his members' bosses to get that cash.

In a dramatic break with the history of his union, he has sometimes sided with Republicans in campaigns — Republicans who are sympathetic to his union's interests.

Using those weapons, he has not only repelled most attempts to curb Medicaid spending, but he has persuaded Gov. George Pataki and lawmakers to expand health-care coverage even in lean economic times. This year, he wants the state to make businesses that don't provide group health insurance to their workers to pay a $3,000-per-employee assessment to the state.

"He's become a national figure on the strength of what he's been able to do in Albany, largely with New York state taxpayers' money," said E.J. McMahon of the Manhattan Institute, a business-backed think tank.

Rivera sees his role in different terms.

"We're fighting for the health care of the people of New York, and for the welfare of our members," he said.

It makes sense for Rivera, who has been president of Local 1199 of the Service Employees International Union since 1989, to go after politicians rather than health-care institutions because Medicaid accounts for one-third of all health-care spending in the state.

In fact, the state and federal governments provide hospitals directly with 70 percent of their income, and through their influence over insurance rates they have effective control over the rest, said Kenneth Raske, president of the Greater New York Hospitals Association and a Rivera ally in the fight to get more money out of Albany.

"It's clear that most of the controlling factors in health care emanate from government — either Albany or Washington," Raske said. "Government really affects the health-care system more than any other industry.''

So rather than use the traditional union tools of strikes, boycotts and other job actions, Rivera's union buys TV ads, lobbies, contributes to campaigns and sends thousands of its members into the streets, distributing pamphlets and running phone banks either directly for the issues they're pushing or for candidates they're supporting.

Raske said the alliance he has struck with Rivera is unique, giving them together far more power than their peers in other states.

"People all over the country are really amazed when we talk about it," Raske said.

"Basically we have an understanding that both management and workers get up in the morning and try to improve health care,'' Rivera said, when asked to explain the alliance.

Rivera is in a unique position to influence state government, an analyst who follows state and city politics closely said.

"Rivera has a strong hand that he plays very well," said the analyst, Fred Siegel, of the Progressive Policy Institute, a Democrat-leaning think tank. "He has what both parties need: the troops. Neither party has a ground operation anymore. Dennis realized that and he stepped into the vacuum.''

The TV ads are also an important weapon, Siegel said.

"When he ran the ads (in 1996, opposing Medicaid cuts) he scared the hell out of the Pataki people and they haven't challenged him since,'' Siegel said.

Flexing muscle

The union has a string of successes to show for its efforts:

• In 1994, his union beat back an attempt by then-Gov. Mario Cuomo to cut Medicaid spending by $400 million, and did the same thing two years later when Pataki tried to make cuts.

• In 1999, as part of an alliance with hospital owners, he and his allies spent $10 million on TV commercials pushing a plan to raise the state cigarette tax by 55 cents a pack to pay for health insurance for those who couldn't afford it. Pataki and the Legislature approved it.

• In 2002, the union and hospital management teamed up again to persuade Pataki and the Legislature to spend an extra $3 billion on health care over four years, much of it for raises for Rivera's members, even though the state was looking at a multibillion-dollar deficit. The deal again raised cigarette taxes and assessments on health-care providers.

Later that year, Rivera stunned Democrats by endorsing the Republican Pataki, whom he calls a "close friend," in his campaign for a third term over Democrat H. Carl McCall — the first time the union had ever backed a Republican for governor.

This year, in a weak economy with the state facing a multibillion-dollar deficit, Rivera and his hospital allies are trying to persuade Pataki and the Legislature to enact the new fee on businesses that don't offer their workers group health insurance.

Rivera views the plan as a way to "stop freeloaders from passing on the cost of health care to taxpayers.''

But the head of the state's leading small-business group said the plan would unfairly penalize small entrepreneurs and others already struggling with the high cost of doing business in New York.

The idea is a "well-intentioned but poorly thought out plan that could only do damage to the small-business community," said Mark Alesse, head of the state chapter of the National Alliance of Independent Businesses.

Strong organization

Behind Rivera are the 250,000 members of his union, who pay 2 percent of their salaries in dues. The average salary is $38,000 and the maximum dues are $75 per month. Half of them also have agreed to pay $5 a month into the union's political action fund.

"We have $1.5 million in the bank, and more money is coming in every month," said Rivera's top political aide, Jennifer Cunningham.

Rivera's union and its hospital allies last year spent more than $11 million trying to influence the state — almost five times more than the next biggest spenders, New York State United Teachers. In contrast, Alesse's group spent only $230,000.

Cunningham said the union is pressing constantly to get more members to pay into the political action fund. It is also trying to sign up new members, with 30 full-time organizers in the field, mostly upstate.

There are about 600,000 health-care workers in the state, "and our goal is to represent every single one of them,'' Rivera said, adding that the union is adding 15,000 to 20,000 new members a year.

"He's always pushing," McMahon, of the Manhattan Institute, said of Rivera. "He won't be stopped until everybody runs out of money.''

The trouble is not that Rivera and his union are so aggressive, Siegel said, but that there's no strong political weight on the other side of the issue to balance the debate.

"We're a public-sector-run state,'' he said. "Wall Street is our biggest industry, but it's completely detached from the rest of the New York state economy. To the extent that they are attached, they're wealthy and powerful enough to cut their own deals. So there's no counterforce (to Rivera) in Albany. That's a deep structural problem New York has.''

Pataki hasn't said whether he supports the new health-care levy on businesses.

Rivera is also playing his cards close to the vest on the issue, declining to say when he'll start TV ads and other steps to push lawmakers to adopt the plan.

"If we fail to get it this year, we'll keep fighting,'' he said.