California, the most populous state in the country, has the highest number of remaining uninsured of the states that expanded Medicaid. Of the states that have not expanded the program, Texas has the most people still uninsured -- 4.425 million.
Of those Californians still uninsured but not eligible for benefits under the ACA, about half (922,000 people) are undocumented immigrants and by law cannot qualify for benefits. The rest either have an income too high for a subsidy or they have an offer of health insurance from their employer.
These estimates are compiled from the 2015 Current Population Survey of the U.S. Census Bureau. They are similar to another estimate from researchers at UCLA and UC Berkeley, known as CalSIM (California Simulation of Insurance Markets).
Prof. Gerald Kominski, an author of that estimate, said the CalSIM modeling showed about 500,000 fewer people eligible for Medi-Cal and 500,000 more people in the undocumented group, but overall the two estimates "are in the same ballpark."
The challenge will be reaching those still without insurance, Kominski said. The remaining uninsured who are eligible for Obamacare benefits are people who have sat out during the two open enrollments since the Affordable Care Act went into effect in 2014.
Kominski said that for families with mixed immigration status, where some members are lawfully present and others are not, there's "ongoing concern ... that trusting the process will not result in information being shared" with immigration authorities. Some other people, he said, may have a distrust of government.
James Scullary, a spokesperson for Covered California, said that "there's no question" the remaining uninsured will be a more challenging population to reach, but he also pointed to Covered California's success so far in signing up those eligible.
As noted above, 16 percent of the remaining uninsured are eligible for Covered California subsidies. Only five states have a better enrollment rate than California (Arizona, Illinois, Maryland, New Jersey, New Mexico).
Scullary said Covered California is "right in the middle of taking a look at the various models. ... We have not settled yet on an official number of our own."