When the program began a decade ago, states could offer coverage to families whose income was not more than double the federal poverty level. Today, for example, that threshold is $41,300 for a family of four. A few states use a Medicaid-based formula that lets them insure more children than under the income limit. Already, 18 states exceed the 200 percent level, with federal permission.

Five more, including California, plus the District of Columbia, could join the list this year, according to a survey by Georgetown University's Center for Children and Families. New York lawmakers recently set an income limit of up to $82,600 for a family of four. Eligible families get some government help in buying insurance. The poorer they are, the greater the subsidy. Other states considering significant expansions in eligibility include California, Ohio and Oklahoma. Florida and Oregon are considering modest expansions, the center reported.