Congressional leaders and Democratic presidential candidates are proposing huge investments in undergraduate education, including tuition-free public college and larger grants for students from low-income families. Although those policies would reduce the need to borrow for certificates and associate’s and bachelor’s degrees, they ignore the staggering debt Americans amass in graduate programs.

A paper released Monday by the liberal think tank Center for American Progress suggests that a failure to address mounting graduate debt could undermine efforts to make higher education more affordable. Even if people can earn a bachelor’s degree at little to no cost, those savings could become inconsequential if they pursue an advanced degree.

The rise of expensive graduate programs, a dearth of grant aid and unlimited lending by the federal government have increased the prevalence of graduate school borrowing. The trend is often overlooked because borrowers with graduate degrees are not defaulting in droves, although they may be burdened with high-interest, high-balance debt for decades.

The paper explores policies that could lower graduate debt, including borrowing limits, pricing caps and penalizing schools for saddling too many students with debt they cannot repay. Some reforms could weed out degrees with poor returns but might also restrict access for marginalized groups or lower the quality of programs.

“A lot of these ideas are provocative and some wouldn’t work,” said Ben Miller, author of the paper and vice president for postsecondary education at the Center for American Progress. “But we need to have this conversation. I worry about what we’re doing to people’s ability to build wealth.”

Graduate programs account for 40 percent of federal student loans issued each year, with borrowing increasing by $2.3 billion from the 2010-2011 academic year to 2017-2018. By comparison, borrowing for undergraduate programs declined by $15 billion during that period. The rise in graduate debt reflects, in part, robust enrollment, which grew 39 percent from 2000 to 2017, according to the National Center for Education Statistics.

In some cases, graduate schools create expensive online programs to subsidize other academic offerings, researchers say, a practice enabled by the federal policy that allows graduate students to borrow up to the full cost of attendance. Employers, Miller said, also bear responsibility for a “lazy desire for graduate degrees” that are not necessary to excel at a job. Demanding advanced degrees, he said, means colleges seek to meet the demand.

Policy analysts have debated the merits of capping graduate borrowing, but Miller and others say they worry that stricter loan limits could create a larger market for private loans with poor terms. Setting limits on federal loans could also depress enrollment of people of color, who may be shut out of private credit markets.

Graduate school has become an expensive path to parity for people of color. Economist Marshall Steinbaum has said African American students pursue advanced degrees to gain equal footing in the job market with whites who hold bachelor’s degrees. Their graduate school debt is often compounded by loans they took out for undergraduate studies. Any policy addressing graduate debt would need to take equity into consideration, Miller said.

He argues that nearly unlimited lending by the federal government has made it easy for schools to offer credentials with prices out of step with earnings expectations, such as a master’s in social work that has a median debt of $115,000 and first-year earnings of barely $50,000.

“We have a disconnect between the credentialing system we’ve established and the pay system that is trapping borrowers in the middle, and there should be a conversation about how to solve that,” Miller said.

The paper published Monday explores the controversial idea of judging graduate schools by their students’ debt to earnings, something akin to the gainful employment rule the Education Department once used to regulate career-training programs.

Before the Trump administration eliminated the regulation, about 60 percent of the programs that had debt-to-earnings ratios above acceptable levels closed to avoid the possibility of losing access to federal student aid. Although Miller does not advocate cutting off financial aid to graduate programs, he said programs could be subject to loan limits.

Suzanne Ortega, president of the Council of Graduate Schools, a trade group, said any such regulatory regime would be difficult to execute because of the complexities of graduate education.

“Developing any system that would be sufficiently nuanced to take into account regional variations, employment mobility, degree difference, evolution in the workforce over time . . . would be extraordinarily complicated,” Ortega said. “Universities are taking a step in this direction themselves with a commitment to career transparency.”

Graduate schools, Ortega said, are providing more information about career outcomes to help students make informed decisions. She said solutions to tackling graduate debt must involve employers and states.

Many social workers and teachers, for instance, must complete graduate coursework to keep their jobs or increase their pay, but their compensation falls short of what’s needed to pay off debt. States with credential requirements should provide options that could be repaid with a reasonable share of a teacher’s or social worker’s salary over a set time, Miller said.

College Scorecard data released last summer by the Education Department cast a light on graduate programs in which students leave with six-figure debt but earn nowhere close to what they owe. An analysis of the data by Robert Kelchen, an associate professor of higher education at Seton Hall University in New Jersey, found the average median debt for master’s degrees was $42,335. For doctoral degrees, it was $95,715. Professional degrees in fields such as law and medicine can result in debt of more than $141,000.

One way to lower the expense of medical training would be for Congress to increase scholarship funding for the National Health Service Corps, a federal program that covers up to four years of medical or dental school in exchange for service in an area with a shortage of health-care providers.

To bring down costs for law students, Miller suggests schools shift from a three-year program to two years, which would mean reducing the number of required credits. These kinds of field-specific approaches could be easier to execute than price caps on programs, he said.