Graduates attend commencement at University of California-Berkeley on May 16. (Noah Berger/Reuters)

The $1.3 trillion burden of student debt is becoming an issue in the 2016 presidential campaign as candidates court the millions of Americans grappling with the high cost of college.

Congressional Democrats are advocating for debt-free public higher education and pushing party front-runner Hillary Rodham Clinton to take up the issue in her campaign.

White House hopefuls Sen. Bernie Sanders (I-Vt.) and former Maryland governor Martin O’Malley have already backed the plan, with Sanders proposing his own federal program to make four-year public college free.

Republican contenders have not laid out any specific positions, but New Jersey Gov. Chris Christie, Sen. Marco Rubio (Fla.) and former Florida governor Jeb Bush have framed the issue as a barrier to economic mobility in recent speeches.

“We’re talking about over 40 million Americans who have student debt,” said Sarah Audelo of the Center for American Progress. “We have this multi-
generational impact . . . and there has to be a conversation.”

The latest data from the New York Federal Reserve shows that 65 ­­percent of student loans are held by Americans younger than 39, while people age 40 to 59 hold another 30 ­percent.

The issue weighs heaviest on the minds of millennials, who have endured soaring college costs that forced many to take on tens of thousands of dollars in debt. A Harvard University Institute of Politics poll found that 57 percent of people under 30 believe that student debt is a major problem for young people.

Democratic pollster Geoff Garin, who worked on Clinton’s 2008 campaign, said he thinks the issue of student debt is as important to millennials as “war and peace issues” were to baby boomers.

“A part of the reason student debt is so important for Democrats is that it’s a crucial motivator to get younger people to vote,” Garin said. “Student debt is often the defining economic fact of their lives.”

People 18 to 34 account for about one-fourth of the voting-age population. While that group largely sat out the midterm elections, their votes proved critical in the last two presidential elections.

Although it is early in the campaign season, Democrats are making a clear play for the millennial vote. They have introduced a slate of resolutions calling for the elimination of student debt at public colleges, the increase of federal grant aid and reduction of interest rates on student loans. It is part of a larger push to promote debt-free college as a campaign issue.

“Student debt will be a central issue in the 2016 elections, both at the presidential election and the congressional level,” Sen. Elizabeth Warren (D-Mass.) told reporters at a Howard University event in April. “There are two problems that have to be solved: the high cost of college education and huge outstanding student loan burden. And we need to go after both of them.”

The debt-free college initiative is based on a plan sketched out by liberal think tank Demos. It calls for the federal government to award grants to states that increase spending on higher education and increase need-based grant aid. That way, fewer students would have to take on high debt loads to attend public colleges.

Mark Huelsman, senior policy analyst at Demos, called the plan “a return to the promise of higher education as a public good.” He said it is the sort of big idea, much like universal health care, that’s built for a presidential campaign, the grounds to test out a platform that could shape future policy.

Building on the Demos plan, Sanders introduced a bill last week for free tuition at four-year public colleges and universities. He would have states pony up $1 for every $2 the federal government invests in higher education. The federal share of the money would come from taxing transactions by hedge funds, investment houses and other Wall Street firms. All told, the plan would cost $70 billion a year.

Since many popular solutions for reducing student debt involve more government spending, it is an issue that the Republican Party has largely shied away from, said Lanhee Chen, a Hoover fellow and Mitt Romney’s policy director during the 2012 campaign.

But Chen said that shouldn’t preclude candidates from touting ideas to provide graduates with quality jobs to repay their debt or supporting online learning as a way to reduce costs and completion time.

“The answer to how to get people prepared for the jobs of this economy is not, let’s just throw free school at them,” he said. “The right response is, are we providing the proper avenues to ensure that students are getting access to the education they need to be productive members of the economy?”

There are no Republican Party initiatives comparable to the debt-free college plan, but conservative leaders say there are a number of proposals that GOP candidates can support to gain a toehold with young voters.

High on the list is a set of ideas floated by the American Enterprise Institute’s Andrew Kelly. One proposal would make colleges pay a percentage of their graduates’ defaulted student loans to give schools more of a stake in student outcomes. Another would establish a legal framework for income-share arrangements that let private investors pay students’ tuitions in exchange for a guaranteed percentage of their future incomes.

“The crisis of college affordability has marched up the income spectrum in a way that it hadn’t in past cycles, and it’s going to be a defining issue for the middle class,” Kelly said. “Republicans have ceded a lot of the ground to the Democrats on this. They’ve made the issue about how much we spend rather how we spend it. And that’s been a mistake.”

Of all of the Republican presidential contenders, Rubio has been the most vocal on student debt. The Florida lawmaker has backed income-share lending as an alternative to student loans, and he supported the expansion of online learning.

Rubio also introduced a bill with Sen. Mark R. Warner (D-Va.) last year to simplify federal student loan repayment by placing borrowers into a plan that automatically deducts 10 percent of their earnings every month. Unlike the current Pay as You Earn plan, the bill placed a $57,500 cap on loan forgiveness after 20 years — a move that could hurt grad students.

While the bill gained little traction in Congress, it did establish Rubio, who finished paying off his student loans in 2012, as someone concerned about the plight of students.

On the whole, Republican candidates have been more inclined to support cuts to higher education.

Earlier this month, congressional Republicans passed a budget that would eliminate guaranteed funding for Pell grants, which provide money for the country’s poorest students to attend college. The budget plan also reverses the expansion of income-based repayment and gets rid of a federal program that forgives any remaining student loan debt for borrowers who work in the public sector for 10 years.

Although the budget resolution is unlikely to become law, it sends strong signals that Republicans are taking aim at higher education. In fact, two presumptive presidential candidates, Wisconsin Gov. Scott Walker and Louisiana Gov. Bobby Jindal, have each proposed hundreds of millions of dollars in cuts to their state higher education budgets.

“There is an argument for fiscal responsibility,” said Peter Wehner, a senior fellow at the conservative Ethics and Public Policy Center. “And then there is an argument for saying: ‘Look, just because the Democrats decided they want to spend record levels and you put the brakes on that doesn’t mean you are an enemy of students.’ ”