For these people, Medicaid coverage is mandatory. There are other groups for whom the state has the option of providing Medicaid benefits. These include certain aged, blind or disabled adults with income below the poverty level, institutionalized persons with limited resources, and other groups, as determined by that state.
Laws vary from one state to another.
Recent reforms in welfare have also changed some of the rules regarding Medicaid. So you'll need to speak with a representative in your state Medicaid office, for more details.