Most 2020 Democratic candidates agree it’s time to do something to make college more affordable for Americans. To that extent, most of them want to get rid of tuition for some kind of higher education. But that’s where the agreement ends.

The next front is what to do about people already out of college who have student loan debt. Economists say 45 million Americans have a total $1.6 trillion in debt, which is causing friction on the economy.

Some candidates have suggested getting rid of student loan debt for either poorer Americans, some Americans or — in the case of Sen. Bernie Sanders (I-Vt.) — all Americans.

Sanders unveiled his bold plan Monday. He did it in his capacity as a senator, proposing legislation called the College for All Act. But the timing, and Sanders’s status in the top tier of Democratic presidential candidates, seems intended to one-up his 2020 opponents.

The bill goes much further than any of the other candidates are proposing to do as president. Some moderate Democrats question the wisdom of student debt forgiveness because it would be giving taxpayer benefits to Americans who are more educated and tend to earn more money, reports The Post’s Jeff Stein.

That Sanders introduced the bill days before the first presidential debates all but guarantees it will be a topic of conversation. So here’s the rundown of the main student loan debt ideas in the 2020 Democratic primary and the biggest supporters of forgiveness. We’ve listed them in order of least expansive to most.

Make community college free: “I wish I could staple a free college diploma under every one of your chairs — I do,” Sen. Amy Klobuchar (D-Minn.) said at a CNN town hall in April. “Don’t look. It’s not there. I wish I could do that, but I have to be straight with you and tell you the truth.”

Klobuchar’s new addition to the education system would be to make community college free, something President Barack Obama proposed. But she mostly wants to work within the existing system by allowing students to refinance their loans at low interest rates and expanding Pell Grants.

Make public college free for lower-income people: South Bend, Ind., Mayor Pete Buttigieg wants to make public colleges tuition free for lower-income families and “affordable for all,” according to a paragraph on his website that is scant on detail.

Make public college free for everyone and forgive loans for people who have received welfare or food stamps: Julián Castro, Obama’s former housing secretary, would get rid of tuition at public universities, community colleges and vocational schools. In fact, free public college has become the baseline for the more liberal members of the primary, and every candidate on the list from here on out has suggested it.

For those already out of college, Castro would forgive loans for people who have received some kind of public assistance, like Medicaid or food stamps for any three years within a five-year period.

Make public college free for everyone and cancel student loan debt for most Americans: Like Castro, Sen. Elizabeth Warren (D-Mass.) wants to get rid of tuition at public colleges. She also wants to cancel up to $50,000 in student debt for people who earn less than $100,000. She estimates that would get rid of about 95 percent of student loan holders’ debts. Debt forgiveness alone would involve a one-time cost of $640 billion. Warren plans to pay for the plan with a 2 percent annual tax on 75,000 families with $50 million or more in wealth.

"The time for half-measures is over,” Warren wrote on Medium.

Make public college free for everyone and cancel all student loan debt: There’s an estimated $1.6 trillion of student debt in this nation, and Sanders wants to get rid of all of it.

“This is truly a revolutionary proposal,” he said. He’d pay for this with a tax on stock and bond trading. His proposal comes alongside a bill introduced in the House of Representatives by leading liberal members, Reps. Ilhan Omar (D-Minn.) and Pramila Jayapal (D-Wash.).