Twenty-two governors, all Republicans, have already sent notice that they won’t build their own exchanges. The rest have until Dec. 14 to decide.

No more than three or four additional states are expected to build exchanges themselves, according to estimates made by Bryce Williams, a managing director at the consulting company Towers Watson, in a phone interview last week.

Nationwide, health plans will be required to meet certain minimum qualifications for participating in the exchanges, such as offering sufficient networks of doctors and hospitals and meeting federal limits on out-of-pocket costs. The law lets states set additional rules.

Being Selective

In states that already have many competing health plans, “the exchange can afford to be a little more selective, versus a state where there aren’t that many health plans, or the politics are such that they don’t believe in as active a state role,” said Jon Kingsdale, a former executive director at the Massachusetts’ health exchange and a managing director at Wakely Consulting Group, an adviser for five of the six states that won approval.

Maryland may establish stricter rules aimed at driving down health-care costs, “at the point we have the market behind us,” Pearce said. The state’s marketplace has already drawn interest from 10 companies, including UnitedHealth and Aetna Inc., and will be open to any plan that meets the federal minimum rules, with a few technical modifications, until at least 2016, she said.

Connecticut will require all health plans to commit to sell plans in its exchange for at least two years, and they face a two-year “lockout” period if they exit the exchange, said Counihan, the CEO of the state’s exchange. Plans will also have to include at least 90 percent of the state’s federally funded health clinics in their networks, a rule aimed at protecting low-income people, he said in an interview.

Massachusetts’s Health Connector, the exchange that has operated in that state since 2006, has added carriers even as it imposed rules that include requiring insurers to offer standard benefit packages, said Glen Shor, the executive director.

“We work very closely with all of our insurers to structure rules that empower consumers but make it as easy as possible for insurers to work with us,” he said in a telephone interview. “It is a delicate balance to strike.”

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