Democratic presidential candidate, Sen. Bernie Sanders, I-Vt., speaks during a town hall meeting at Nashua Community College in Nashua, N.H., Saturday, June 27, 2015. Credit: AP Photo/Michael Dwyer

Democratic Presidential contender Bernie Sanders has a radical plan to overhaul how the government funds higher education: abolish tuition altogether at every public college in the country. Most of the money to do so would come from what he calls a “Robin Hood tax” – a tax that takes from the rich to give to the poor. But his chief adversary, Hillary Clinton, calls that plan a giveaway to rich families.

“I don’t think taxpayers should be paying to send Donald Trump’s kids to college,” she said during the second official Democratic debate, Saturday night in Des Moines, Iowa.

While Sanders and his supporters acknowledge that his plan would benefit rich families who send their kids to elite public colleges like the University of Virginia or the University of California at Berkeley – schools with acceptance rates and facilities that rival many moneyed private schools – they say the upshot would be countless more Americans making it to and through college.

Some experts see the wide range in quality between the commuter college down the road and the public flagship university as a major stumbling block for the Sanders idea of importing a European free-college model.

“In many states the public flagships have left the educating of low- and middle-income students to open-access institutions like community colleges,” said Mark Huelsman, senior policy analyst at Demos. “That’s why we at Demos have proposed a condition, that these institutions have to be representative of their state populations.”

“I just wonder if this will pull even more upper-middle class families, who would have gone to private schools otherwise, into public colleges, because it’s hard to beat free.”

Sanders’ plan comes with a $70 billion a year price tag – the total amount public colleges collectively charge in tuition. To put that in perspective, that’s more than twice what the federal government currently spends on its largest education budget item – the Pell grant program, which provides financial aid to over eight million poor undergraduates. The federal government would cough up two-thirds of the $70 billion by instituting a tax on some financial transactions; the rest would be left up to the states.

Clinton has criticized Sanders’ plan as a handout to wealthy families who, she insists, can – and should – foot some of the bill themselves. Clinton’s plan would essentially readjust the current aid system by increasing aid, particularly to poor and middle class families. Clinton projects that her plan would cost half of Sanders’ plan – about $35 billion a year over 10 years.

Related: There’s finally federal data on low-income graduation rates – but it’s wrong

Mark Kantrowitz, a consultant who specializes in the nation’s financial aid system, predicts that either amount would be a non-starter in the Republican- controlled House of Representatives.

“This idea that just pouring in federal money is going to fix all the barriers low-income kids face is just wishful thinking.”

While both Clinton and Sanders have spoken extensively about the importance of increasing the number of Americans with college degrees – both for the economy and for individuals– they are essentially speaking two different languages. Clinton makes a financially driven argument; Sanders calls for a broad philosophical shift in how the government treats higher education. Tapping the words of 19th century Republican president Rutherford B. Hayes, who called for free universal education through high school, Sanders argues that in the 21st century, the government should provide a system of free public colleges to everyone — essentially establishing the right to a bachelor’s degree.

Beyond those high-minded sentiments, supporters of Sanders’ plan also see a more tangible advantage – more poor kids will think college is possible under a system with the clear and simple message that public colleges are free for everyone.

“My take is I’m willing to give away a little bit to people who can afford it, to get more for low income students,” said Sara Goldrick-Rab, a professor of educational policy studies at the University of Wisconsin at Madison, who supports not only free tuition but also making sure that students don’t go into debt for living expenses. “The idea is that while some of the giveaways will flow upward to wealthier families, most of the benefits would flow down to the low-income students who need it.”

Matthew Chingos, a senior fellow at the Urban Institute, questions whether making college free for the one in five public college students whose families earn at least $106,000 a year is a good use of scarce tax dollars.

Related: Communities come together to increase college-going from the ground up

“There’s this tension between what is a good use of public money and giving the most access possible,” said Chingos. “I just wonder if this will pull even more upper-middle class families, who would have gone to private schools otherwise, into public colleges, because it’s hard to beat free.”

The estimated cost of Bernie Sanders’ proposal to make college free for every American is $70 billion a year. Hillary Clinton’s plan to make college more affordable has an estimated cost of $35 billion a year.

Chingos points out that 93 percent of families making more than $106,000 a year currently pay at least some of the sticker price for public colleges. Goldrick-Rab argues that with $20,000-a-year price tags at some public universities, even those families need help.

Both Chingos and Goldrick-Rab agree that any financial aid program must look beyond just tuition and consider what students, particularly poor students, spend on essentials like rent and groceries.

Andrew P. Kelly, director of the American Enterprise Institute’s Center on Higher Education Reform, thinks that federal policymakers should wait and see what comes of state programs that guarantee free college for all.

“Tennessee is doing this on their own, and I am interested to see whether it pays off in terms of gains in educational attainment, and if it does, we will have to see what we can learn from them,” said Kelly. “But this idea that just pouring in federal money is going to fix all the barriers low-income kids face is just wishful thinking.”

This story was produced by The Hechinger Report, a nonprofit, independent news organization focused on inequality and innovation in education. Read more about Higher Education.