So far, though, only 23 states and the District of Columbia plan to participate in the Medicaid expansion. The remaining states are mostly led by Republican governors who refuse to go along with expansion.
Low-income individuals in states that do not expand Medicaid eligibility will not be penalized for not having health coverage. But the poorest among them -- people living below the poverty line -- won't be able to access federally subsidized coverage through the state health exchanges, either. That leaves nearly 10 million of 15 million potentially eligible adults without coverage, according to a recent Associated Press analysis of Urban Institute data.
"This rips the heart out of health-care reform because it denies access to America's most vulnerable," said Lawrence Gostin, professor of global health law at Georgetown University School of Law.
Will the health exchanges open in time?
Another 24 million people will be enrolled in health plans through the state health insurance exchanges by 2023, according to a Congressional Budget Office estimate. The administration hopes to enroll 7 million people in the first year of eligibility.
Recently, though, Congress' Government Accountability Office reported that health officials are running behind schedule on many aspects of health exchange formation, including testing data systems that will be used to determine eligibility for coverage.
On Friday, the Obama administration published regulations scaling back the requirement that state health insurance exchanges, or marketplaces, verify consumers' income and health insurance status to obtain coverage under the law. Instead, the exchanges will rely more heavily on self-reported information until 2015, according to the Washington Post.
In a recent interview with CNBC, Todd Park, chief technology officer with the U.S. Department of Health and Human Services, said the state health insurance exchanges are "on track" and will be up and running on Oct. 1 for open enrollment.
Self-reporting will streamline the enrollment process, said Dan Schuyler, director of exchange technology at the Salt Lake City-based consulting firm Leavitt Partners. But, he added, "it also opens the door to deliberate fraud, abuse and unintentional eligibility errors."
Is Obamacare in trouble? Depends on whom you ask
Republican opponents of the Affordable Care Act assert that the Obama administration is playing politics by delaying provisions of the law, particularly the employer mandate, until after 2014 mid-term Congressional elections, The Hill reported.
By 2023, the law will reduce the number of people without health insurance by 25 million, still leaving 31 million uninsured, according to Congressional Budget Office (CBO) estimates.
House Budget Committee Chairman Paul Ryan (R-Wis.) wants the CBO to reevaluate the estimate of the law's impact in light of the recent delays, according to The Hill.
Alden Bianchi, group leader of the law firm Mintz Levin's employee benefits practice in Boston, doesn't believe recent changes suggest the federal law's implementation is in trouble, as Republican opponents assert.