As Democratic presidential candidates promote billion-dollar plans to make college free on the campaign trail, advocates for affordable higher education across the political spectrum are pushing a simpler approach: Look to the states.

One state in particular — a Southern, reliably Republican one — has risen above the rest, lawmakers, education and policy think tanks told NBC News: Tennessee.

The Volunteer State's "Tennessee Promise" program, passed in 2014 by the GOP-controlled legislature and signed into law by then-Gov. Bill Haslam, a Republican, offers two years of tuition-free community college or technical school to all high school graduates. An expansion of the program adopted in 2017, called "Tennessee Reconnect," guaranteed two years of free community college or technical school to all adults in Tennessee who didn't already have a degree or credential.

Republican Gov. Bill Haslam speaks at a press conference at the state Capitol in Nashville, Tennessee, on Dec. 1, 2015, about his plan to grant more autonomy to six public universities in the Tennessee Board of Regents system. Erik Schelzig / AP file

"Regardless of what your politics are, you have to admit that income inequality is an issue. The question is what do we do about it. And I am a firm believer that a robust public education is the key. The great equalizer," Haslam told NBC News in a recent interview. “If a good education is a requirement to enter the workforce, we have to give more people the opportunity do that.”

How it works

Tennessee's program is considered a "last dollar" scholarship, meaning that, after all other aid (including federal grants and scholarships) is factored in, the funding covers the remaining balance for tuition and mandatory fees. The program is available to all high school graduates, regardless of income status, and provides every student with a mentor to guide them through the application, financial aid and enrollment process. It also requires that all students complete eight hours of community service each semester, measures supporters say provide some accountability.

Tennessee Promise is funded entirely by an endowment that was created from the state’s lottery reserve fund. No tax increases were needed at any point, a crucial draw for state Republicans.

But even more critical to the program's success was the fact that Haslam, who left office in January, framed it as an economic issue centered on job creation in his state — a strategy top education officials in Tennessee are encouraging national politicians to embrace.

“We needed more Tennesseans with a credential beyond high school,” said Mike Krause, executive director of the Tennessee Higher Education Commission — the state's de facto head of higher education.

The program has drawn plaudits from conservatives — who say that higher education policy is (and should be) governed principally by the states — and progressive groups, who have praised its simplicity and inclusivity.

Could the program work nationwide?

While its "last dollar" nature makes it dependent on available federal aid — which would seem to inherently preclude it from being used as an exact model for a national plan — education experts say many of its chief tenets should still be part of any effort to reform higher education and higher education debt-related policies.

“There's a real appetite among people to have an education that gets them into the workforce. And a free associate's degree from a community college is a really amazing route to go,” said Jessie Ulibarri, the executive director of the State Innovation Exchange, a progressive policy shop that helps draw up model state legislation that advances traditionally progressive issues.

“The idea of a free public education has broad appeal,” he added. “The fact that states like Tennessee are finding creative ways to do this shows that this doesn’t have to labeled just a progressive idea.”

Local and national advocates say the program has been wildly successful thus far, and point to a series of statistics to prove it: Community college enrollment is up, as are overall college attendance, completion and retention rates.

According to data on the program collected by Tennessee state agencies, the FAFSA filing rate, which unlocks key federal aid dollars, rose substantially, too. And overall, student debt in the state has declined. (In 2018, Tennessee had the 10th least amount of average student debt, according to data analyzed by the nonprofit Institute for College Access & Success, while the group’s 2015 study showed that Tennessee had the 16th least amount of average student debt).

Tennessee's achievement, which the Obama administration once cited as an example in its own national push for free community college, has spurred the creation of similar programs in at least a half-dozen other states, such as Oregon and Rhode Island.

Critics, however, have pointed to the fact that Tennessee Promise and programs like it are not explicitly geared toward low-income populations, whose barriers to higher education also include substantial nontuition expenses like food, housing and books. (The Debt-Free College Act, proposed by Sen. Brian Schatz, D-Hawaii, and endorsed by 2020 hopefuls Sens. Elizabeth Warren, Kamala Harris, Cory Booker and Kirsten Gillibrand, is one proponents say best addresses the needs of low-income students, since it would cover nontuition costs like books and living expenses.)

“That is really the area where many of them need additional support, and Tennessee's plan doesn’t cover that,” Mamie Voight, the vice president of policy research at the Institute for Higher Education Policy, said.

Advocates acknowledge that, but point out that the process for accessing higher education in the U.S. is so comprehensively flawed that it makes sense to have a need-blind universal program, explaining that simple messaging and the elimination of cumbersome paperwork, or providing assistance with it, attracts the greatest amount of people.

“The way we talk to students — all students — about financial aid just doesn't work. We assume they know what FAFSA is, what Pell Grants are, but they don't,” Krause said. “And in devising this program, we knew that if we wanted Tennesseans to go to college, we were going to have fundamentally shock the system and give these kids a streamlined process.”

“Having broad-based programs that expand opportunity for everyone, period, regardless of your financial circumstances, is a really good way to go,” Ulibarri said.

He added that practicality and results matter, too — saying that while he is a fan of broader, more expensive plans being pushed by the likes of Warren and Sen. Bernie Sanders, Democratic candidates should also try to be realistic by focusing on the creation of similar state-level programs.

Proposals like Tennessee's have been endorsed by 2020 Democrats Beto O’Rourke, Sen. Amy Klobuchar and Julián Castro — something that Haslam, despite being a Republican, suggested their competition might want to heed.

“I'm not sure they’re going to listen to me, but I would say, 'Go look at what is actually happening, and what is actually working,'” he said.