The Hill reports of the nearly 2 million who now lack coverage, most are either younger adults or people who bought policies on their own.

Gallup, for its part, says those younger adults saw a big drop in their number who are uninsured since 2013, but as Republicans wrangle over the repeal-and-replace struggle to kill the Affordable Care Act and replace it with something which will kick either 23 million (House version) or 22 million (Senate version) off coverage in the next 10 years, the reversal to an upward trend looks likely to continue.

Related: Unpopular Senate health care bill assailed by study, medical groups

Says Gallup: "Several marketplace factors could be contributing to the uptick in the uninsured rate since the second half of 2016. Rising insurance premiums could be causing some Americans to forgo insurance, especially those who fail to qualify for federal subsidies."

Furthermore, some insurance companies are leaving the ACA marketplace, and the lack of competition could be driving up the cost of plans for consumers. There's considerable uncertainty over whether the Trump administration will authorize cost sharing reduction (CSR) funds provided to insurers under the ACA. The uncertainty of receiving CSR funds — which help to balance costs among insurers with sicker, older patients with the costs experienced by insurers with younger, healthier (and more profitable) patients — has already caused a number of insurers to exit the marketplaces.

Gallup adds "[u]ncertainty surrounding the healthcare law" could also be pushing the number of uninsureds higher, especially since Trump's executive order allowing nonenforcement or delay of ACA provisions that "impose a fiscal burden" on individuals, in addition to the potential for a Republican replacement law that could eliminate or simply not enforce any penalties for not buying insurance is likely to convince some fence-sitters decide to wait it out and not buy coverage.

Related: CDC reports on uninsured Americans 

The penalties were put in place to boost participation by the young and those in good health who might otherwise just not carry health coverage. However, their participation under the ACA is part of what makes the health care law work: younger, healthier people with policies help to offset the costs of older, less healthy people.

Under either Republican plan, the older and less healthy would be hit with huge price increases and/or denial of coverage for preexisting conditions, either one of which could shut them out of being able to obtain any coverage at all.