The race is on to sign up uninsured Americans for health-care coverage this fall, with a number of large national advocacy groups launching aggressive, multimillion-dollar campaigns this summer aimed at promoting President Obama’s health-care law.

The groups are buying television ads, tapping social networks, training hundreds of new workers and volunteers and developing online and on-the-ground efforts akin to an enormous, months-long get-out-the-vote campaign. They aim to raise awareness in preparation for a big push leading up to open enrollment Oct. 1, when people can begin signing up for insurance plans and government subsidies available under the law.

“We’ll be engaging Americans in their homes and communities, getting mothers talking to children, neighbors talking to neighbors, friends talking to friends about the changes and what the new law means to them,” said Anne Filipic, president of Enroll America, a group that on Tuesday launched a campaign called “Get Covered America.”

The nonprofit coalition of advocacy organizations, health insurers, hospitals, pharmaceutical companies and others sprang up in conjunction with the law. It has ties to the White House, has raised tens of millions of dollars since February and plans a seven-figure television ad buy in the fall.

Planned Parenthood, the National Council of La Raza, the Service Employees International Union and Organizing for Action — the Democratic political-action group that grew out of Obama’s campaign apparatus — are also mobilizing this summer, along with many smaller groups. Their aim will be to spread awareness of the law’s benefits and persuade generally healthy people who lack coverage to sign up.

The groups’ work will be critical to the success of Obama’s signature domestic accomplishment, the 2010 Affordable Care Act, which is aimed at dramatically reducing the ranks of the uninsured over the next decade — by providing subsidies to low-income people to buy private plans and by expanding Medicaid, the state-federal health insurance program for the poor.

The government has struggled to promote the law, because of widespread confusion about its provisions and because of political opposition. In a call with reporters Tuesday, Filipic — a former Obama campaign organizer and White House staffer — said the group’s research shows that 78 percent of uninsured people do not know about the changes coming in January.

That is when the law’s subsidies and Medicaid expansion — as well as the mandate that virtually every American carry health insurance or face a tax penalty of $95 in the first year — kick in.

The Obama administration is gearing up for its own awareness effort. It has secured an $8 million contract with the public relations firm Weber Shandwick and will launch a Web site this summer for people to register for online accounts and shop for health plans. The administration is also setting up a call center that will be open around the clock and be able to assist callers in 150 languages.

Congress has repeatedly rebuffed the administration’s requests for more money to help set up the health-care law, which is why the work performed by Enroll America and others will play such a critical role.

The coalition includes major players in the health world, including Aetna, the American Heart Association, Catholic Charities and CVS Caremark, as well as many nonprofits mounting their own independent efforts. The group has a presence in 18 states and will be holding strategy sessions and handing out information at farmers markets and churches this weekend.

Enroll America has come under fire because of its close relationship with the administration. Last month, Republicans mounted an inquiry into solicitations by Health and Human Services Secretary Kathleen Sebelius for donations to the group. Her actions have fueled questions about whether money is scarce to promote the health law and raised questions about Enroll America, which has sought to remain nonpartisan.

Ronald Pollack, executive director of Families USA and the founder of Enroll America, said the Sebelius controversy did not significantly damage the organization. He said he believes the discussion around the health-care law will evolve away from politics this summer as people try to figure out how it will affect their lives.

“What needs to happen in the weeks and months ahead is to help everyone understand how their personal circumstances will be affected by the Affordable Care Act as it gets implemented on January 1,” he said.

Outreach efforts will be crucial because officials do not expect the tax penalty to be a motivator for people to sign up for coverage. The White House is banking on 2.7 million young, healthy people signing up for insurance in the first year to offset the cost to insurers of all the sick people expected to rush to enroll.

Many advocates say this goal is attainable, especially with the help of the nonprofit and advocacy groups.

For example, Planned Parenthood serves some 3 million people nationally — more than half of whom are in the 20-to-29 age range — and estimates that half are uninsured. The group is printing posters and magnets to hand out to patients at its health centers across the country and is training workers to help patients navigate their insurance options.

Organizing for Action on Monday announced that it has purchased a seven-figure cable television ad buy aimed at raising awareness about enrollment options. The group has enlisted the help of about 800 unpaid fellows who will be serving as on-the-ground organizers, and it also has a vast e-mail network estimated at about 13 million people.

Young Invincibles, a youth-oriented organization that formed to help pass the health-care law, expects to train 1,000 community groups on how to help people find insurance. It is developing a mobile phone app that, among other things, will send reminders when it is time to sign up for insurance.