Hillary Clinton, buckling to pressure from her left, recently proposed tuition-free college education. Students who attend in-state public colleges and universities, and whose families have incomes less than $85,000 a year, would qualify for varying levels of assistance. This threshold would rise to $125,000 by 2021. The students would have to work 10 hours a week. Federal grants, matched by state contributions, would finance the program. Estimates of the cost to the federal government over 10 years range from $350 billion to $700 billion.

Though the proposal is still only an outline and lacks important details, it already has at least five serious deficiencies that make it infeasible.

• Because more than a few states will likely choose not to participate, the proposal offers false hope to millions of future students. Tuition at public colleges and universities has escalated in large part because state legislatures have chosen to shift more of the tuition burden from taxpayers to students and their families.

Under the Clinton plan, states would have to make a policy U-turn. This politically difficult decision would be even harder for financially strapped states. Many legislatures would find it nearly impossible to generate the billions of dollars needed to match federal grants.

• The proposal excludes tens of thousands of students of equal need who are ineligible because they attend private colleges. This number could grow, as needy students are crowded out of public colleges by an influx of applications from well-off students who otherwise would have attended private universities.