Massachusetts and Connecticut share a border and both have Democratic governors, yet when it comes to signing residents up for insurance through President Obama's health care law, the two states are polar opposites.

Between the launch of Obamacare last Oct. 1 and the end of February, only 12,965 people in Massachusetts signed up for insurance through the state's exchange, according to data released on Tuesday by the Department of Health and Human Services. That represents just 6.5 percent of the 200,000 who were projected to enroll through February in HHS's original projections.

In stark contrast, the much smaller state of Connecticut signed up 57,465 people for Obamacare -- more than double original forecasts.

The extreme cases of Connecticut and Massachusetts demonstrate the wide variation among states when it comes to signing up for Obamacare, variations that cannot be explained merely by population size or which political party is in charge.

The variation is important, because for all the attention given to the national numbers, the success of Obamacare will hinge on how it's doing at the state level. Each individual state has its own risk pool and that pool must have a critical mass of participants and enough young and healthy enrollees to be sustainable.

Overall, 13 states overcame early technical challenges and have seen enrollment exceed original HHS projections made in September, weeks before the exchanges opened. But 38 states (including the District of Columbia) have missed their targets.

In 12 states, sign-ups are tracking at less than 50 percent of the target, and 24 states are at less than two-thirds — though Illinois was off by less than one percent.

In D.C., despite the influx of congressional staffers who were kicked off their insurance as a result of the law, only 6,249 people had enrolled -- or 18.2 percent of the target.

Though supporters of the health care law have accused Republican governors of trying to sabotage Obamacare, arguing that it would work better in states where it had the strong backing of the state government, that isn't showing up in the enrollment numbers.

Some of the worst-performing states (such as Massachusetts, D.C., Oregon, Maryland and Washington) enthusiastically embraced the law. At the same time, states with Republican governors such as Florida, North Carolina and Wisconsin are among the states beating expectations.

In total, HHS reported that 4,242,325 million Americans had signed up for coverage through February, which represents 75 percent of the goal of 5,652,800.

An important caveat to note is that the numbers presented here are charitable to the administration, because they include those individuals who have merely selected a plan, rather than those who have consistently paid their premiums, which is traditionally how enrollment is measured. HHS still hasn't released data that takes into account those who have paid, but insurance industry sources have estimated that the number of non-payers is in the 20 percent to 25 percent range, which would reduce total enrollment by around 800,000 to 1.1 million.