That turn of events reflects an aggressive strategy by a national nurses union, experts say: Its members are growing in numbers, and they have not been afraid to walk picket lines. The huge costs of hiring temporary nurses – and likely bad publicity – have forced institutions like the hospital center to return to bargaining on staffing and wages.

National Nurses United, the largest nurses union in the country, has helped organize strikes or threatened them this year at hospitals in California, Pennsylvania, Maine, Michigan and Minnesota. The Oakland, Calif.-based union has tapped into concerns of registered nurses worried about losing jobs at a time when hospitals and health-care organizations are under enormous pressure to cut costs.

“They have been very aggressive in legislative lobbying efforts, influencing public policy through informational picketing, and willingness to get out there and strike,” said Joanne Spetz, an economist who specializes in nursing workforce issues at the University of California at San Francisco. “Love them or hate them, you have to respect their success.”

The union also sported a high-profile campaign during the recent midterm elections by attacking Republicans for their positions on health care. They targeted Meg Whitman, who lost to Jerry Brown in California’s governor’s race, and Sharron Angle, who was defeated by Democratic incumbent Harry Reid in Nevada’s Senate race.

The voluble face of National Nurses United is executive director Rose Ann DeMoro, a former Teamsters organizer who took over the California Nurses Association in 1993 and boosted its membership fivefold. DeMoro, also a vice president of the AFL-CIO, which includes NNU as an affiliate, envisions a superunion of the country’s 3 million registered nurses.

Aggressive tactics?

“Absolutely,” she said. “If you are going to advocate for nurses and patients, and if you are meek, these hospitals will roll right over you.”

For nurses, changes in the delivery of and payment for care are occurring at the same time that patients are sicker than before and the use of sophisticated technology is increasing. Coupled with chronic understaffing and high turnover, the pressures on nurses are enormous.

Still, the willingness to walk a picket line is not universally embraced. Some nurses think unions are unprofessional and strikes pose a conflict to a nurse’s ability to advocate for patients. But others, like National Nurses United, believe “if you don’t yell and scream, you’re not going to get anything,” Spetz said.

Formed late last year when the 86,000-member CNA and other state nurses unions joined forces, the NNU claims 155,000 members, gaining ground on the century-old American Nurses Association, a professional organization that favors a more collaborative approach.

Unions may be on the decline elsewhere, but NNU can’t keep up with demand, DeMoro said.

NNU’s biggest display of muscle took place in Minneapolis when 12,000 nurses from 14 Twin Cities hospitals, wearing red T-shirts, staged a one-day strike in June, the largest nurses’ strike in U.S. history, the union said.

A longer strike in July was averted with a last-minute settlement that preserved pension and health benefits but failed to meet the union’s demand for strict nurse-patient ratios. Instead, the hospitals agreed to examine staffing in existing committee systems; the union is pushing for legislation to set ratios.

Nurse-patient staffing is the signature issue for the union. Nurses have complained for two decades that there are not enough nurses in hospitals to provide high-quality care. It is also a strategy that appeals to broad public sympathy for nurses – and ratios guarantee jobs.

In Lansing, Mich., a last-minute agreement late Thursday between an NNU member and Sparrow Hospital averted a one-day nurses strike set for Monday. The tentative agreement includes changes in health and retirement benefits, a modest increase in wages and increased nurse staffing, according to a joint statement by the hospital and union.

The hospital faces financial penalties if it fails to meet specific ratios, NNU spokesman Chuck Idelson said. DeMoro hailed the agreement as an “enormous victory for patients.”

In Bangor, Maine, nurses are moving ahead with a one-day strike, also planned for Monday; officials at Eastern Maine Medical Center, Maine’s second-largest hospital, locked the nurses out Saturday.

In Washington, NNU, representing 1,600 nurses, has filed a complaint with the District health department saying that chronic understaffing at the 926-bed hospital has compromised patient care. The hospital denies the charge, calling it a scare tactic.

Studies show a correlation between higher levels of experienced nurse staffing and better patient outcomes, but there are no national standards for specific ratios.

Only California mandated nurse-patient ratios, starting in 2004. Of 14 other states and the District that have laws or regulations on nurse staffing, seven states require hospital committees to set staffing, according to the ANA, which supports a hospital committee approach.

Maryland and Virginia have no legislation requiring staffing by ratio or by a hospital committee, the ANA said.

Maybe not for long.

“I think you’re likely to see a lot of organizing” in the Washington region, said NNU’s DeMoro. “We’re very anxious to change the laws.”

Officials at Washington Hospital Center, the region’s largest private hospital, say staffing goals are as good as or better than those in California.

In medical-surgical units, for example, each nurse is supposed to care for no more than four to six patients, compared with the California workload of five; in intensive care units, the ratio is one to one, better than California’s 1-to-2 ratio.

WHC officials emphasize that staffing is fluid, adjusted constantly depending on the number of patients and how sick they are. Nurses say, however, that staffing goals are often unmet, especially on nights and weekends.

“We have reviews of staffing constantly, and we have never had unsafe staffing,” said Janis Orlowski, the hospital’s chief medical officer.

WHC nurses had been represented by a local nurses union. After the contract expired and talks stalled in July, the hospital imposed its best offer Oct. 1, angering nurses. Days later, the nurses voted to affiliate with NNU. In quick succession, the union filed the complaint with the health department, and about a week after that, nurses voted for a one-day strike.

The hospital has said it would remain open, with full service, during a strike. It needs about 600 nurses a day and had planned to hire temporary nurses. Officials told striking nurses they would be out for five days, not one, because the hospital was obligated to pay temporary nurses for a minimum of 60 hours of work.

In the event of a strike, other labor unions would support the nurses by refusing to cross the picket line to make deliveries, NNU’s DeMoro said.

Some nurses were initially put off by the new union’s more aggressive tactics and distrusted the AFL-CIO affiliation, according to one nurse with more than 20 years’ experience. She did not want to be identified for fear of retaliation.

She had voted to strike. But after NNU and the hospital announced Wednesday that the strike was off and wage cuts were postponed, she and many others were relieved, even hopeful.

“I think this is going to get resolved,” she said. “I think it’s a good thing. It’s given us a lot more power.”