Nearly 46 million people in America lack health insurance, according to the U.S. Census Bureau, and the cost to the country adds up to tens of billions of dollars.

Directly or indirectly, the states pick up much of this tab. Uninsured individuals flood state-subsidized clinics and emergency rooms. States also bear the treatment costs for chronic illness among the uninsured. And a population that is not well cannot function to full capacity, hampering a state’s productivity.

The issue is so pressing that in the last two legislative sessions, more than a dozen states have moved to overhaul coverage for the uninsured. In the absence of federal policy or Washington leadership ready to take on the issue, more and more states are making the uninsured a top priority.

Late last month, Vermont became the third state to approve near-universal health insurance. Crafting the Catamount Health plan required three years of wrangling among the state’s Republican governor, Democratic-majority legislature, top state officials, doctors, insurance providers and private citizens.

Vermont Secretary of Administration Michael Smith said a single imperative propelled this cumbersome process: “We all agreed that if we didn’t start curbing these costs, we were going to be broke.”

The Vermont experience reflects a growing national trend, said health care analyst Laura Tobler of the National Conference of State Legislatures: “States are moving ahead with reform because there is no momentum at the national level.”

A lack of federal action also has prompted new state laws encouraging greater use of renewable energy and limiting green-gas emissions. Several states have filled a federal law vacuum on the use of stem cells. And with no movement in Washington, some states have moved to raise their minimum wage.

With health insurance, legislators are responding to clamor from voters who say they cannot afford the kind of regular medical maintenance it takes to stay well – and really cannot afford treatment if they get sick. State lawmakers know they keep their jobs by creating policy that people want and need, Tobler said.

As large and small employers slash insurance benefits – sometimes eliminating coverage entirely – much of the states’ efforts are directed at the working poor. Health insurance premiums also have climbed so high that some people cannot afford coverage even when they are eligible, Tobler said.

“The uninsured have always been there, but states now are moving ahead to cover them,” she said.

The means by which states tackle the problem vary, but generally involve an attempt at universal health insurance, a public-private insurance partnership or a revised implementation of Medicaid, the state-federal shared program that provides insurance for low-income people, the disabled or those who need long-term nursing care.

Medicaid, conceived in the Johnson administration, grew in spite of itself to become “an unplanned substitute for people who didn’t have coverage,” said professor Robert Blendon of the Harvard School of Public Health. Most states that have addressed the insurance question have taken the Medicaid route, shifting funds from Medicaid or redefining eligibility.

To steer these measures into existence, some lawmakers and governors must overlook sharp differences. The overwhelmingly Democratic legislature of Massachusetts, for example, worked diligently with Republican Gov. Mitt Romney to draft the nation’s most comprehensive insurance package. The bill became law in April.

Along with Maine, Massachusetts and Vermont – the only states with universal coverage plans – Arkansas, Florida, Oklahoma, Tennessee, Kentucky and Montana passed recent laws that seek to reduce the ranks of the uninsured. Iowa, West Virginia, Hawaii and New Mexico also have enacted measures targeting this issue.

Maine kicked off the trend three years ago with the Dirigo health plan, designed to provide universal coverage in a small state with a large working-poor population.

Today, even its most ardent supporters call Dirigo a work-in-progress because so few people are enrolled – around 10,000. Dirigo was intended to bring coverage to 130,000 uninsured or underinsured Maine residents over a five- to six-year period. About half of those on its slender roster were previously uninsured, and the remainder were underinsured.

The plan, which did not get off the ground until early 2005, was touted as a vehicle for employees and owners of small businesses to reduce insurance costs. But some business owners have shied away, saying it is no cheaper than private plans.

Already, however, the Massachusetts program has become Romney’s national calling card. Touring the country as he explores a bid for the 2008 Republican presidential nomination, Romney touts his state’s plan as a potential model – even before it has gone into full operation.

Some other states – including Florida, Kentucky, West Virginia and Idaho – have rearranged the way Medicaid money is spent rather than setting up state-sponsored insurance systems. These states promote their approach as a way to encourage consumer choice and foster personal responsibility.

But Cindy Mann, director of the Center for Children and Families at Georgetown University’s Health Policy Institute, said the real goal is to reduce state spending, not to expand coverage.

“They are, at best, moving chairs on the deck,” Mann said. “They all seek to limit the states’ spending on Medicaid. So there is a risk that there will be reductions in coverage.”

Many of the new insurance plans take advantage of a federal waiver that provides subsidies to states that reduce their uninsured populations. Some states also have devised creative financing schemes. Starting next month, for example, Vermont will boost cigarette taxes to help fund Catamount Health.

This state-subsidized plan aspires for near-universal coverage and will be sold by private insurance companies. Vermont also approved a companion bill that addresses chronic disease treatment.