According to a recent report...

... 49% of the 32.3 million nonelderly Americans who did not have health insurance at the start of 2015 are eligible for financial assistance. Of those:

• 17% are adults eligible for Medicaid
• 10% are children eligible for Medicaid or the Children's Health Insurance Program
• 22% are eligible for premium tax credits to purchase coverage through the Marketplace

Source: "New Estimates of Eligibility for ACA Coverage among the Uninsured," The Henry J. Kaiser Family Foundation, October 13, 2105, http://kff.org/uninsured/issue-brief/new-estimates-of-eligibility-for-aca-coverage-among-the-uninsured/?utm_campaign=KFF:%202015%20October%20ACA%20Uninsured%20Eligibility&utm_source=hs_email&utm_medium=email&utm_content=22790255&_hsenc=p2ANqtz-9oPzaSj1CFCOGc01MKFpk1I2M_DDr_zf1gTddY494ETI_4iKiIwukUbOy3suQtQMjEaH7rfRhCcSHih-0eVXrxTA8cvg&_hsmi=22790255