The core part of President Barack Obama's health care overhaul takes hold Tuesday, putting the embattled plan to a new test as tens of millions of Americans who don't have insurance can start signing up for coverage.
The Democratic-led Senate rebuffed last-ditch efforts by House Republicans on Monday to derail the health care law—dueling that brought the government to the brink of a partial shutdown. But even if the government is forced to partially close, the rollout of the health care program will go on as planned.
The Affordable Care Act, passed three years ago, marks the biggest expansion of the U.S. social safety net 1965, when Congress created the Medicare health insurance program for the elderly.
The law requires all Americans to have health insurance or face fines, and it provides subsidies to help those with lower incomes to pay for it. It also bars insurance companies from denying coverage to people because of previous illness, though that provision doesn't take effect until Jan. 1.
The law has been contentious from the start. Polls show most of Americans are wary of it, especially the mandate that all Americans have health insurance.
But the law has survived the Supreme Court, a battle for the White House and rounds of budget brinkmanship. It now faces the judgment of American consumers, who can begin shopping for coverage in insurance markets that will open around the country Tuesday.
People will get to find out if they can afford the premiums, if the coverage will be solid, where the bureaucratic pitfalls are and if new federal and state websites will really demystify shopping for health insurance. Full answers may take months.
The rollout is expected to get off to a slow start, with some bumps.
Obama has stepped up efforts to sell the American public on the program. But he has had to delay a key part for one year: a mandate that large employers provide health care coverage. On Thursday, the government announced delays for small businesses seeking to buy insurance online.
People who don't have access to job-based health insurance can start shopping right away for subsidized private coverage. Or they can wait to sign up as late as Dec. 15 and still get coverage by Jan. 1.
Many will probably want to see how it goes for the first wave of applicants before they jump in.
A Kaiser Family Foundation survey found that people are in a fog about what the law means for them. Nearly three-fourths of the uninsured were unaware of the new insurance markets opening to serve them.
Eventually, at least half the nation's nearly 50 million uninsured people are expected to get coverage through the law, either through subsidized private plans sold in the new markets or an expanded version of the Medicaid program for the poor. Immigrants in the country illegally will be the largest group remaining uninsured.
The success or failure of the health care overhaul could well definite Obama's legacy.
Republicans oppose the plan is an intrusion into private decision-making. They also argue cost of the plans is forcing smaller employers to kill full-time jobs.
The Obama administration says the reform is long overdue in the only major developed nation without a national health care system.
Even with the new program, there will be no a single, government-run health insurance covering all Americans. Instead, the program relies on health insurance marketplaces in every state to provide options for people who don't have job-based coverage, who can't afford an individual policy or have a health problem that would disqualify them under the current system.
Explore further: Administration: 'Obamacare' to offer more choices