Under an income-based repayment, if you make little money, you repay little money. If you make nothing, you owe nothing, and your loan doesn’t go into default. The loan forgiveness provision protects borrowers from too much interest accumulating over time.

In 2010, Barack Obama was president, and he, too, pushed a financial aid overhaul through Congress. This time, the government-subsidized private sector loan program was entirely shut down.

Important changes to the income-based repayments were made, but because they were passed under the same legislation that created the Affordable Care Act, few people paid much attention to them. IBR had been made even more generous. Now borrowers had to pay only 10 percent of their income per month, even as the forgiveness threshold was lowered to 20 years. People who work in government or nonprofits are still eligible for forgiveness after a decade. Although it was originally slated to become effective in 2014, Obama administration lawyers found a way to effectively speed up the IBR start date by several years. Most important, all students would now borrow directly from the federal government and be eligible for the more favorable repayment terms.

At first, uptake was slow. Students have to apply for IBR, and it took time for the Education Department to spread the word.

But the latest numbers show a powerful shift. By the third quarter of the 2013 federal fiscal year, only 6 percent of federal borrowers, representing 14.4 percent of the Education Department’s outstanding loan portfolio, were enrolled. Since then, awareness has grown and the numbers have surged. By the end of 2014, the number of borrowers in IBR had nearly doubled, to 11.8 percent. Those borrowers had larger loans on average and represented almost 25 percent of all federal direct student loan dollars owed — over $100 billion. As loans made before IBR was put into effect continue to come off the books, the new system is sure to grow.

We appear to be in the middle of a rapid transition in how student loans are repaid, one that is moving the federal government into the same role that state governments played for much of the 20th century: the foundational provider of broad, unqualified subsidies for higher learning.