Rhode Island, Washington and New York saw enrollment increases of 12.1 percent, 7.8 percent and 4.2 percent, respectively. Meanwhile West Virginia and Louisiana experienced dramatic enrollment declines of 19.5 percent and 23.5 percent, respectively.

In three of the states –– Rhode Island, Washington state and Louisiana –– state officials instructed insurers to focus their rate increase on silver-level plans ("silver-loading") because it is the cost of those plans that determines the size of federal tax credits.

"The tax credit increase caused by silver-loading made gold and bronze plans significantly cheaper not only for consumers who qualified for cost-sharing reductions, but for all consumers who qualified for premium tax credits," write the study authors.

The study also drew a link between the amount of competition in the ACA marketplace and enrollment. When there is more competition, there is more advertising and therefore more awareness among consumers of the ACA exchange.

State efforts to promote or encourage enrollment, including through social media campaigns, appeared to have had an impact, the study found.

Finally, the report hypothesizes that local political rhetoric and local news coverage likely shaped people's understanding of the marketplace.

In Rhode Island, Washington state and New York, local leaders engaged in prominent efforts to defend the ACA and promote its accomplishments. In states where political leaders loudly opposed the ACA and supported federal repeal efforts, many consumers likely believed the law had been repealed and that ACA marketplace coverage was no longer available.

Granted, Louisiana and West Virginia aren't the best examples of anti-Obamacare states, since Louisiana's governor was elected on a platform largely based on expanding Medicaid and West Virginia, despite total GOP control of state government, has expanded Medicaid in the early days of Obamacare and has not taken meaningful steps to undo it.