Insurers that initially fought President Obama's health-care overhaul are funding a group planning to spend $100 million to help the uninsured buy insurance through state marketplaces, called exchanges.

WASHINGTON — Aetna and other insurers that initially fought President Obama’s health-care overhaul are reversing course, funding a group planning to spend $100 million to help the uninsured get coverage under the law.

Enroll America, a nonprofit created two years ago, has gathered support from the insurers that opposed the law and consumer organizations such as Families USA, based in Washington, D.C., that supported it. The new organization plans a broad-based educational campaign to make uninsured people aware of the health-care law’s benefits and help them sign up, said Ron Pollack, Enroll America’s chairman.

The group will reach out to the 43 million uninsured whose participation will help strengthen the funding formula that holds the 2010 Affordable Care Act together. The new customers are expected to help offset added costs for the insurers from new regulations and taxes included in the law.

“Business people in the end have to be pragmatic,” Robert Laszewski, a health-insurance industry consultant based in Alexandria, Va., said of the companies’ efforts to help the law succeed. “The industry has gotten over it.”

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After October 2013, uninsured Americans will be able to buy insurance through state marketplaces, called exchanges, which will be run somewhat like online travel services. People who don’t get insurance through their employers will be able to use the exchanges to shop among a selection of health plans from private insurers, often with taxpayer-subsidized premiums.

About 9 million people are expected to enroll in exchange plans in 2014, according to the Congressional Budget Office, increasing to 26 million by 2018. The exchanges also will route people with incomes close to the poverty level into Medicaid, projected to enroll 41 million people in 2014.

“You want to mimic the success of employer plans, in which everyone is enrolled when they take a job,” said Sara Collins, a vice president at the Commonwealth Fund in New York, in a telephone interview. “It will be essential that everyone comes in to get the coverage that they’re eligible for.”

The federal government has encouraged states to build and operate their own exchanges. Republican governors in 16 states had refused as of Nov. 19 and will let the Obama administration build their exchanges instead, according to the nonprofit Kaiser Family Foundation, based in Menlo Park, Calif.

Rachel Klein, Enroll America’s executive director, said the group may target states whose governors have said they won’t build exchanges or expand Medicaid, such as Texas, home to about 12 percent of the nation’s uninsured. So far the group has raised about $6 million, she said in an interview.

The $100 million the group seeks to raise in 2013 and 2014 will be used for advertising and social media to make people aware of the law’s benefits and help them sign up, said Pollack, who also is executive director of Families USA.

People going to the exchanges for the first time probably will need help, he said, and the government will hire guides to assist the sign-up process.