Insurance markets, or exchanges, are one prong of Obama's law, providing subsidized private coverage for middle-class households who currently can't get their own. The other major piece is a Medicaid expansion to serve more low-income people. And at least 13 states have already indicated they will not agree to that.
"It could look like two or three different countries," said Robert Blendon, a Harvard School of Public Health professor who studies public opinion on health care. "The political culture of a state is going to play an important role in getting millions of people to voluntarily sign up."
Civic leadership from governors, legislators, mayors and business and religious groups is shaping up as a huge factor in the launch of Obama's plan, particularly since the penalty for ignoring the law's requirement to get coverage is as low as $95 the first year.
People-to-people contacts will be key, and the potential for patchwork results is real.
"Obviously it's a possibility in terms of there being some real difficulties," said Sen. Bob Casey, D-Pa., whose efforts helped pass the law. Casey also said he believes the Obama administration will be ready to lead in states holding back.
Disparities already are cropping up.
Town Meeting Day the first Tuesday in March is a storied tradition in Vermont, and this year it provided a platform to educate residents about their options under the health care law. As many as 250,000 may eventually get coverage through Vermont Health Connect, as the state's marketplace is known.
"Even before we were a state, these town meetings existed," said Sean Sheehan, director of education and outreach. "It's a way people come together as a community, and we are counting on those community connections to get the word out." The health care plan was on the agenda at about 100 town meetings, and other local gatherings are taking place.
Texas residents are entitled to the same benefits as Vermonters, but in the state with the highest proportion of its population uninsured, Gov. Rick Perry will not be promoting the federal insurance exchange, a spokeswoman said. Nor does Perry plan to expand Medicaid.
The result is a communications void that civic and political groups, mayors, insurers and hospitals will try to fill.
"You have people who aren't really charged up about it because they don't even know that they would qualify," said Durrel Douglas, spokesman for the Texas Organizing Project, an activist group. A national poll this week by the nonpartisan Kaiser Family Foundation found that two of every three uninsured people don't know enough about the law to understand how it will affect them.
Supporters of Obama's law in Texas say the federal government hasn't shown up yet to launch the state's insurance exchange and no one is sure when that will happen.
"It is a much bigger lift here," said Anne Dunkelberg, associate director of the Austin-based Center for Public Policy Priorities, which advocates for low-income people. "The sooner the federal exchange can get engaged and working with all the folks here who want to promote enrollment, the better."
The Congressional Budget Office predicts a slow start overall, with only 7 million gaining coverage through the exchanges next year, rising to 24 million in 2016.
At a recent insurance industry meeting, federal officials directing the rollout rattled off a dizzying list of deadlines. Public outreach will begin in earnest this summer and early fall, said Gary Cohen, head of the Center for Consumer Information and Insurance Oversight.
The government sees three main groups of potential customers for the new insurance markets, he said.
There's the "active sick and worried," people who are uninsured or have pre-existing medical conditions. Under the law, insurers will no longer be able to turn the sick away.
There's the healthy and young. "They feel invincible, they don't feel a need for health insurance," said Cohen.
Finally, there's the passive and unengaged. "For these people, a significant education effort needs to happen," he said.
To keep premiums affordable, the government will need to sign up lots of people from the last two groups to balance those in poor health, who will have a strong motivation to join.
The official heading consumer outreach for the rollout, Julie Bataille, acknowledges the challenge but says she's confident.
"This is a really an enormous opportunity for us to change the conversation around health care and help individuals understand the benefits they can get," she said.
A closer look at Obama's health care overhaul
O The Patient Protection and Affordable Care Act is the biggest safety-net legislation since Medicare and Medicaid in 1965.
Enrollment starts Oct. 1; coverage takes effect Jan. 1.
It will move the U.S. closer to other industrialized nations that provide health care for all. About 30 million uninsured Americans will eventually gain coverage, at an estimated cost of $1.3 trillion from 2013-2023. Insurers won't be able to turn away people with health problems.
The law mandates that most individuals have health insurance, provides subsidies to help pay premiums and penalizes people who can afford coverage but don't get it. It imposes penalties on businesses with 50 or more full-time workers that don't offer coverage.
Health insurance exchanges set up in each state will offer subsidized private health plans to middle-class households. Medicaid, the government's health insurance for the poor, will be expanded to cover low-income people making up to about $15,400 for an individual. States can opt out of the Medicaid expansion.