In many cases, the high-risk pools were overburdened financially, leaving many people without insurance or with tight restrictions on coverage. Insurers refused to cover the individuals who were likely to have the highest expenses, like those who had H.I.V. or serious kidney disease, and the pools lost money.

Many states had to turn applicants away — in some states, only a small percentage of those who applied received coverage — and the insurance was sharply limited to control spending.

In Washington, over 80 percent of the people referred to the state’s high-risk pool never got health insurance, said Mike Kreidler, the state’s insurance commissioner. In California, which relied on lawmakers to allocate money as part of the state budget, there was a waiting list, recalled Richard Figueroa, who was a senior administrator for the program.

The pool operated on a first-come-first-served basis, Mr. Figueroa said, without regard to people’s income or the severity of their medical condition.