What will debt-free college mean for public colleges?

At the Democratic National Convention, Bernie Sanders argued that the Democrats came together to support debt-free higher education for all students in American public colleges and universities. The Democratic Platform pledges the party to “making debt free college a reality.” To achieve this goal, Democrats support “bold new investments by the federal government, coupled with states reinvesting in higher education and colleges holding the line on costs.”

The question, of course, is how will debt-free college be achieved.