The Affordable Care Act, aka Obamacare, is back in the news as the 2015 open enrollment season gets underway. So far, unlike last year, the roll-out has been smooth. This hasn’t made Republicans a whit more fond of the law. Many want to repeal and replace it.

Just before sign-ups began, liberal pundit and MSNBC show host Ed Schultz challenged Republicans to make good on that line. Schultz said he’s yet to see a fully fleshed out GOP alternative. Several bills spell out key elements of a Republican approach, but their full scope and impact remain unclear. Schultz zeroed in on this lack of precision.

"The Republican agenda seems to want to reverse everything on health care," Schultz said on Nov. 13, 2014. "This is what (Sen. Minority Leader Mitch) McConnell wants to repeal. 10 million people. 10.3 uninsured Americans have received coverage since Oct. 1, 2013. That's a hard number that can be verified."

Schultz picked Oct. 1, 2013, because that was the day the federal health insurance exchange opened (as best it could) for business.

Would, as Schultz said, repeal of the Affordable Care Act take away the health coverage gained by 10.3 million people?

The baseline numbers suggest Schultz is correct.

Between October 2013 and June 2014, Gallup found that 10.3 million nonelderly adults gained health insurance coverage. It’s possible that this number has grown since the data cut off in June 2014.

The New England Journal of Medicine estimated that, through June, 10.3 million adults gained health insurance coverage. Also through June, the Commonwealth Fund estimated the number at 9.5 million. And over the same period, the Urban Institute offered an estimate of 8 million.

An earlier study -- through March -- by the RAND Corp. estimated a net gain of 9.3 million American adults with health insurance.

These are net figures, meaning they include people who may have lost insurance. While there is some fluctuation, they largely support Schultz’s claim.

The more difficult question to answer is, does the Affordable Care Act deserve all the credit?

There are generally three ways people were added to the rolls of the insured since October 2013 -- through an employer, through Medicaid or through federal or state marketplaces. There are scenarios in each category whereby people gaining insurance could see their health care taken away if Obamacare is repealed, and there are scenarios where their health care would remain.

Insurance through an employer

The RAND survey — which will soon be updated — estimated that millions of newly insured Americans got coverage through an employer (Employer-sponsored insurance or ESI).

Why? Partly because of the Affordable Care Act, and partly because the economy is improving and more people are finding work.

"Enrollment in ESI increased by 8.2 million," the RAND analysts wrote, "Most of this increase was driven by people who were previously uninsured. Some of these newly insured individuals may have taken up an employer plan as a result of the incentive created by the individual mandate; others may have newly found a job."

Since employer coverage provides most of the insurance in America, and unemployment dropped during this period, at least a portion of the newly insured would have gained coverage without Obamacare.

However, the lead author of the New England Journal of Medicine article, Benjamin Sommers at the Harvard School of Public Health, said his analysis aimed to factor out the employment impact.

"As best as we could do, without a true ‘control group,’ we were trying to estimate the changes in the uninsured rate attributable to the Affordable Care Act’s first open enrollment period," Sommers said. Sommers said even allowing for job growth, at least 10.3 million people gained coverage due solely to Obamacare.

Insurance through Medicaid

The RAND study also teased out that 3.6 million people relied on Medicaid to get out of the ranks of the uninsured. A major goal of the Affordable Care Act was to expand Medicaid by raising the income eligibility cut-off line to 138 percent of federal poverty. According to an analysis from the Urban Institute , virtually all of the higher Medicaid enrollment took place in the 24 states plus the District of Columbia that chose to expand Medicaid.

Still, some portion of new Medicaid enrollees would have qualified under the previous terms.

How big a portion is unclear, although Medicaid rolls increased by 5 percent even in states that did not raise the income limits.

Insurance through marketplaces

Lastly, the law created federal and state insurance marketplaces where people could pick and choose among private insurance plans. The RAND survey estimated that 1.4 million uninsured people wound up buying insurance this way. The total number is about 4 million, but that includes people who had insurance before.

RAND economist Christine Eibner said the premium subsidies available through the marketplaces have helped millions of people.

"If the ACA were repealed many would lose access to subsidies or Medicaid coverage, and could no longer afford insurance," Eibner said.

However, it’s not entirely clear if all of the 1.4 million uninsured people who purchased insurance wanted it in the first place. Some might have purchased insurance simply because it was required as part of the health care law. In that sense, it’s hard to say their insurance would be taken away if the health care law were repealed.

Other cases of people getting covered

The full impact of Obamacare goes beyond the marketplaces and Medicaid expansion, so the total number could be higher still. In 2012, the law gave parents the option to keep their kids on their health insurance policies until they turned 26. About 2.5 million to 3 million people had taken advantage of the change. However, some of those would have had coverage even without the new policy.

Both Eibner and Sommers, who is a part-time advisor to the Health and Human Services Department, said all told, they believe at least 10.3 million people owe their coverage to Obamacare.

It's hard to get a definitive number, but the estimates we find put Schultz in the ballpark.

Our ruling

Schultz said repealing the Affordable Care Act would take away insurance coverage of about 10.3 million people. Based on multiple independent sources, the combination of the individual mandate, insurance subsidies through the insurance marketplaces, Medicaid expansion and raising the eligibility age for dependents delivers a total that is in the neighborhood of what Schultz said.

But there is a bit of uncertainty in all of the numbers, and Schultz’s suggestion that health care would be "taken away" for everyone is a tad strong. With those caveats, we rate his claim Mostly True.

Correction: A previous version of this story described Sen. Mitch McConnell as Majority Leader. The GOP election wins put him on track to assume the title, but he hadn't yet. He is described as Minority Leader.