The Obama administration is hailing more than 1 million enrollments in health care plans in December alone as a sign that the health care reform law known as “Obamacare” is working. Here’s a closer look at the promise and perils around Obamacare as we enter the year when some of its most important provisions go into effect:

1. What does it mean that 6 million people have enrolled in Obamacare?

It does NOT necessarily mean that 6 million Americans who did not health insurance it 2013 now will have it in 2014. (That would a huge achievement, as an estimated 50 million Americans did not have insurance at some point over the last year)

What the administration has said is that more than 2 million people have signed up, either through HealthCare.gov, one of the state-based websites or on the phone, for private health insurance plans under the law, and another 3.9 million have been deemed eligible for Medicaid or the State Children’s Health Insurance Plan. But it’s important to remember that this number includes some people who had health insurance in 2013 as well, but used the new websites to enroll this year. It also includes a set of people, much discussed this fall, whose previous health insurance plans were discontinued because of the health care law.

Right now, it is impossible to know (and even difficult to estimate) exactly how many people have insurance who didn’t have it in 2013, although the government may have more precise data on this question later in the year. It is also impossible to determine in a comprehensive way if the 2 million people who have new private plans are 1. newly insured or 2. people who had to switch plans and are getting insurance they like better or 3. people who lost their previous plans and are now enrolled in insurance that they are unhappy with, because they had to change doctors, pay more or get reduced benefits.

The Medicaid number is more simple to understand. Unless the law, families of four who make less than $32,000 and individuals who earn less than $16,000 each year are eligible for Medicaid. The administration expected the Medicaid rolls to swell under the law, and they have.

And not just in blue states. Twenty-five states, all but of which has a Republican governor, have so far refused to expand Medicaid under the law. But what data released by the federal government has shown is that tens of thousands of Americans who were ALREADY eligible for Medicaid under pre-Obamacare laws have learned of that status because of all the attention around health care insurance.

So the one obvious conclusion from the data is a large number of relatively low-income people are now getting insurance.

2. So the website(s) works?

Yes. The overwhelming majority of Americans enrolled in health insurance under the law (either newly-insured or replacing their own plan) are using either HealthCare.gov or the site in their state. The 6 million number released by the administration does demonstrate millions of Americans have been able to navigate successfully HealthCare.gov or a state-based website, something that seemed impossible to imagine a month ago.

3. What’s the next problem likely to emerge around the law?

Obtaining health insurance ultimately is just a step in getting medical care and perhaps then improving your health. And the new enrollees have completed the first step, but the next two could be more problematic. Americans will now learn that some of the Obamacare plans are very cheap because they have high deductibles, very limited networks of doctors and hospitals and other limitations.

The other challenge is one for the Obama administration. Obama aides desperately want some young, healthy Americans to enroll in the health care plans, which will help to keep down prices because the younger and healthier effectively subsidize older or less healthy patients. (Under the law, insurance companies can’t charge you a higher rate than someone in same age range because you have some kind of illness already, and are limited in how much more than can charge older customers compared to younger ones.)

The government has not released data on the age mix of the new health care recipients. But anecdotally, it seems many of the people who kept navigating a website that was barely functioning at first were the people most eager to have health insurance, i.e. people who are elderly or have some kind of illness.

But the government predicts that younger people will enroll by March 31, the true deadline for health insurance for 2014. And while Obama administration officials have bungled much of the health care rollout, they did correct predict a surge in sign-ups in December.

4. Is this still a big political problem for the president and Democrats?

It’s hard to tell. The president’s poll numbers dipped in October and November, when coverage of the flawed website and people losing their existing health insurance plans was constant. But Obama is also a second term president facing a Republican Congress opposed to much of his agenda. It’s not clear if he will ever get back to the high approval ratings that came after his reelection. (According to the Pew Research Center, about 55 percent of Americans approved of Obama in December 2012, compared to 45 percent now).

For now, at least the president is no longer apologizing for problems with the health care rollout and can start discussing other issues.

Some Democrats are bullish about the law, arguing Republicans will eventually feel pressured to backtrack on their opposition to it as more and more Americans get insured. I doubt that. In Kentucky, one of the states whose rollout of the Affordable Care Act has been most successful, the politics of the issue have so far not changed at all: Republican Sen. Mitch McConnell, running for reelection there, blasts the law at every turn, while it’s not even on the website of his Democratic challenger, Alison Lundergan Grimes.

It’s hard to imagine most Democrats in swing states or red states campaigning with their support Obamacare as a leading reason to back them.  The best Democrats can hope is that the problems of the rollout are forgotten by Election Day in 2014.

But there is one exception to this: the Medicaid expansion. Polls show that expanding Medicaid is fairly popular, even in strongly-Republican states in the South where GOP governors have opted out of the program.

Democrats running in states where Obama won in 2012, but have a GOP governor, like Florida and Wisconsin, could put Republicans on the spot for effectively declining federal money to insure citizens in their states. Charlie Crist, the Democratic candidate in Florida for governor, is already doing this.

5. Are those Republican governors ever going to expand Medicaid?

Between 5 and 8 million Americans (estimates range widely) would be eligible for Medicaid if their state government opted into the expansion of the program under the health care law. Some Republican governors, like Iowa’s Terry Branstad, are trying to cut deals with the federal government to expand insurance but in ways that are not officially a Medicaid expansion.

But the rhetoric of Rick Perry of Texas, whose state has by far the largest population of uninsured people among the GOP governors, remains very anti-Obamacare. It is hard to imagine he will compromise on that stance in the next year.