“If the American people bailed out Wall Street, now it is time for Wall Street to come to the aid of the middle class of this country,” Sanders said at a press conference.

US student debt has more than tripled since 2006, now at over $1.5 trillion — almost 8 percent the size of the country’s GDP. Meanwhile, real wages are up less than 7 percent over the same period, and rents are up more than 47 percent in real dollars.

Until now, Sanders had not committed to eliminating all student debt, preferring instead to say he would “drastically reduce” it. But today, he came out for full cancellation, saying, “The bottom line is we shouldn’t be punishing people for getting [a] higher education. It is time to hit the reset button. Under the proposal that we introduced today, all student debt would be canceled in six months.”

“It is unjust and it is a burden that no generation before had to encounter to the scale and the level that our generation has,” Ocasio-Cortez said at the same press conference.

In April, Sen. Elizabeth Warren introduced a plan that would cancel about 40 percent of outstanding student debt ($640 billion). Warren’s plan is means-tested, meaning that those with higher incomes — specifically those with household incomes above $100,000 per year — would have less of their debt forgiven, and many would have none forgiven at all. Her plan also capped the amount of debt forgiveness any borrower could receive at $50,000, regardless of income.

Critically, as Jacobin’s Meagan Day pointed out at the time, Warren’s plan “fails to fully cast education as a social right and student debt as essentially illegitimate. [T]his leaves the plan politically vulnerable, because if some student debt is legitimate, then conservative interests will endeavor to broaden that category.”

Some critics have argued that students with larger debts have an obligation to pay them back because they often have higher incomes than those with smaller debts. But today, Sanders made a full-throated argument for universal debt cancellation, marking a clear difference between his style of politics and Warren’s.

“I happen to believe in universality. That means if Donald Trump wants to send his grandchildren to public school, he has the right to do that. Our response to making sure that this does not benefit the wealthy is in other areas where we are going to demand the wealthy and other corporations start paying their fair share in taxes,” Sanders said.

In other words, if billionaires want to use public goods, that’s fine — they should pay for them through taxes, rather than at the point of use. (Of course, Trump’s grandchildren won’t be going to the City College of New York or SUNY Plattsburgh; they’ll head off to the Ivy League and other elite private schools like the ones Trump and his kids attended.)

While Warren’s plan is a vast improvement upon the status quo, it ultimately depends on the government deciding who deserves debt relief, and how much. Such decisions are always, at their base, arbitrary. Does a Wall Street trader making $98,000 per year deserve more debt relief than a pediatric oncologist making $102,000? What about a household of two teachers making $52,000 each? Why?

On the other hand, by making student cancellation a universal demand, Sanders, Omar, Ocasio-Cortez, and Jayapal create what Robbie Nelson has called an “engine of solidarity.”

Constructing engines of solidarity means moving beyond the liberal view of solidarity as a sympathetic disposition and instead binding people together in relationships of shared material interest. It means ameliorating the brutality of life under capitalism while fashioning a working class that is more structurally unified and in closer political conversation with socialist ideas.

Rather than create a pecking order of who deserves more, less, or no relief, engines of solidarity draw their power from uniting the most people under a single demand. Like Medicare for All and College for All, a demand for universal student debt relief unites tens of millions of people around a simple, shared, material idea.

And by funding the debt cancellation with a tax on Wall Street, the proposal directly pits the interests of capitalists and the rich — who have made a killing on student debt interest — against the interests of the poor, working class, and middle class.

Together, these two aspects — near-universal solidarity and a class enemy — advance Sanders’s “class-struggle social democracy” approach to politics. Sanders knows that he can only win with a “working class that is more structurally unified and in closer political conversation with socialist ideas.” Demands like canceling all student debt help to ideologically unify the working class and bring them closer to socialist ideas, if not all the way there.

Unfortunately, making these kinds of bold demands is easier than actually winning them. Sanders, Omar, Ocasio-Cortez, and Jayapal have put universal student loan forgiveness on the table. Grassroots organizers will have to build the movement to win it.