A college education is a basic requirement for many middle-class jobs, but it is increasingly harder to afford. That is why every presidential candidate needs to explain what he or she will do to make higher education attainable for more Americans without them having to take on crippling amounts of debt.

On Monday, Hillary Rodham Clinton, the Democratic front-runner, released an ambitious proposal that aims to help students at public four-year colleges graduate without incurring any debt for tuition. Bernie Sanders, a senator from Vermont who is also seeking the nomination, has gone even further and said that he would make tuition free for all undergraduate students at public institutions. Regrettably, none of the Republican candidates has come up with anything comparable.

Students and their families are paying more for college and going deeper into debt every year. About 60 percent of graduates from four-year public universities had student loans in 2013. On average, they owed $25,600, up 20 percent from 2000 after adjusting for inflation, according to the College Board.

Clinton’s plan aims to reduce college costs for students by giving federal grants to states and colleges and by allowing borrowers to refinance their student loans at lower interest rates. It would reward states that agree to spend more money on higher education and give more money to colleges that reduce expenses, though it does not say what kind of costs should be lowered. It also includes a good proposal put forward by President Obama in January to make two-year community colleges free to all Americans. The plan would cost $350 billion over 10 years, which is close to what the federal government currently spends on Pell Grants. Those grants would continue. Clinton would raise the money by capping unspecified deductions wealthy families can take on their income taxes.

Sanders’ free-tuition plan would offer states $2 of federal money for every dollar they spend on reducing or eliminating tuition. His proposal would cost $750 billion over 10 years, and Sanders says he would raise the money by imposing a small tax on financial transactions. Martin O’Malley, the former Maryland governor who is also seeking the Democratic nomination, has said he has a plan to help students avoid borrowing to pay tuition, but his campaign hasn’t provided an estimate of how much his proposal would cost.

These plans are missing important details, so it’s hard to determine their potential impact. A big unanswered question is how state governments would react. In Congress, conservatives will be especially hostile to any tax increases to help reduce tuition costs. But young Americans buried by student loans want fresh thinking on the crisis, something the Republican candidates have not offered.