As tens of millions of American file for unemployment insurance, about half of those who lose job-based health insurance will be eligible for Medicaid and another 25-30% for ACA marketplace subsidies, according to estimates by the Urban Institute and Kaiser Family Foundation.
The lower percentage potentially picked up by the marketplace is not in itself a knock on that program. In the U.S., regular unemployment insurance income is very low, and normally accessed only by a minority of the unemployed. In the 35 states that have enacted the ACA Medicaid expansion, those with incomes up to 138% of the Federal Poverty Level (FPL) are eligible for Medicaid. People whose current monthly income is below that threshold are expected to make up a large percentage of those losing job-based coverage. The $600-per-week extra unemployment insurance (UI) benefit provided for up to four months by the CARES Act does not count toward Medicaid eligibility.
That said, the marketplace has always been a leaky vessel for those who need insurance and qualify for its subsidies (let alone those who need insurance and don't qualify for subsidies, a group that abandoned marketplace coverage in droves in response to the premium runups of 2017-18). A bit less than half of those who qualify for subsidies enroll, according to the Kaiser Family Foundation's 2019 estimate (which I suspect is a tad low). Takeup of Medicaid is much higher. The Kaiser Family Foundation's 2018 estimate of the uninsured who are eligible for Medicaid (6.7 million) is less than 10% of total Medicaid enrollment (73 million in 2018).
