Gallup researchers said the new data aligns with the reduction Gallup has seen in the national uninsured rate from 2013 to the first days of April. Last week, they reported that the uninsured rate had dropped from 17.1 percent to 15.6 percent between the fourth quarter of 2013 and the first quarter of 2014 — the lowest rate since 2008.

Researchers attribute the majority of the decline in the number of uninsured to the Patient Protection and Affordable Care Act.

The Obama administration announced Thursday that eight million people signed up for coverage under PPACA's exchanges. An additional 3 million people have signed up for insurance through Medicaid.

Critics of the law say that numbers of "newly insured" under PPACA are exaggerated because they account for new coverage plans brought about by the plan cancellations because of the law.

Gallup's findings are based on interviews with more than 20,000 U.S. adults, conducted as part of Gallup Daily tracking from March 4-April 14.

Gallup also said the administration's goal in getting younger Americans to enroll in health coverage through the law has been "modestly successful," as people between 18 and 29 years old accounted for 30 percent of the newly insured. And those between 30 and 49 years old accounted for 38 percent of the newly insured. But both age groups were more likely to buy insurance off the exchanges as opposed to on them.

Additionally, Gallup said though there are younger adults who became newly insured, they aren't necessarily healthier. Using a measure of self-reported health status, Gallup found that the newly insured in 2014 mirror the health of the overall population, meaning they aren't any healthier or sicker than the overall population.

Gallup also, not surprisingly, found the newly insured also tend to be lower-income and are more likely to get coverage through the exchanges, where some of those individuals can qualify for subsides to help them buy insurance.

In similar research out earlier this week, Gallup released further data indicating the PPACA is helping with the uninsured rate.

States that expanded Medicaid and set up health exchanges under PPACA are seeing their uninsured rates drop faster than others, Gallup said. On average, the uninsured rate declined 2.5 percentage points in the 21 states, and the District of Columbia, that have implemented both of these measures, compared with an 0.8-point drop across the 29 states that have taken only one or neither of these actions.

"While a majority of Americans continue to disapprove of the Affordable Care Act, the uninsured rate appears to be declining, as the law intended," Gallup researchers noted.

Also read: Census survey changes cloud PPACA numbers