He and other Democrats pointed Monday to a statement made last week by Moody's Investors Service.
The New York firm said last Thursday that states will face "political and budgetary pressure" to cover the hospitals' loss of federal money for treating uninsured patients.
Moody's estimates hospitals' loss nationwide will be $17 billion a year by 2019. The firm says states that choose not to expand Medicaid may face large uninsured populations while federal payments to hospitals are declining.
Republican Gov. Phil Bryant says Mississippi can't afford to put an estimated 300,000 more people on a Medicaid program that already covers more than 640,000. The state has about 3 million residents.