For years, advocates like myself have been saying that canceling student debt should be a political no-brainer. In addition to being economically smart and ethically just, it would energize voters – especially younger ones.

Tuesday proved us right. Voters under the age of 29 broke for Democrats in overwhelming numbers, helping turn the much-feared Red Wave into a Red Trickle. In a speech on Wednesday night, President Biden acknowledged that student debt relief played a big role in motivating the “historic” turnout of young people, alongside the issues of climate change, abortion and gun violence.

On Twitter, the White House chief of staff, Ron Klain, made a similar point, saying that President Biden “kept his promises to younger Americans (with action on climate change, student loans, marijuana reform, etc), and they responded with energy and enthusiasm”.

The problem is that Klain’s comment isn’t totally accurate. Young people did indeed respond with energy and enthusiasm – to at least one promise that is, to date, unfulfilled. Almost three months after Biden’s cancellation program was announced, not a single person has seen a penny of relief.

And now they may not ever see relief – unless Biden acts. On Thursday night, a Trump-appointed judge in Texas struck down the student loan cancellation program. This hyper-partisan decision will hold unless Biden fights back. Fortunately he has the legal tools to do so.

The stakes are too high, and margins too tight, for the White House to not follow through on this essential commitment. On Tuesday, debt relief almost certainly played a decisive role in key races, including Senate races. Consider Pennsylvania, where cancellation champion John Fetterman beat back the reactionary Dr Oz. In Arizona, Mark Kelly, another proponent of cancellation, exceeded expectations. Not so for Ohio Democrat and Senate hopeful Tim Ryan, who strongly opposed Biden’s cancellation plan and lost to the Trump impersonator JD Vance. Likewise, in North Carolina, the Republican senator Ted Budd trounced Cheri Beasley, who waffled on debt cancellation and, it seems, paid a price.

Ryan’s and Beasley’s cancellation-averse approach was the one many aspiring soothsayers recommended. Ever since Biden took office, professional pundits have vehemently insisted that canceling student debt would turn off middle-aged, middle-of-the road Democrats, when in fact it drew young people to the polls. (Political commentator David Frum, a man who has made his career being wrong about everything, at least admitted he was wrong about this: “I thought student debt relief was bad policy and bad politics. I still think it bad policy – but looking at the youth vote surge, hard to deny its political impact.”)

Looking ahead, there’s no doubt student debt relief will play an outsized role in the 6 December Georgia runoff – a contest that may determine the balance of power in the Senate. Democratic incumbent Raphael Warnock has been a leader in the fight for cancellation, unwavering in his faith that delivering student debt relief is vital to winning the south. Republican challenger Herschel Walker, meanwhile, has denounced Warnock for wanting to help student debtors, who he claims spend their loan money on booze, vacations and video games.

A recent government report shows the absurdity of Walker’s lie: many students only receive one financial aid disbursement per semester, often delivered into banking products with fees so high they are pushed into overdraft; students reported that this led to the need to fast, use candles for electricity, or forgo textbooks and gas. In addition, polling shows that 29% of student debtors will spend less on basic needs – food, housing, bills – should the pandemic student loan payment moratorium end.

If Biden wanted to give Warnock a boost, he would cancel student debt tomorrow and let Walker deal with the fall out. Imagine the jubilation and appreciation unleashed when tens of millions of people see their balances reduced or entirely wiped out,1,506,100 Georgians among them. Young people might once again turn out in droves, and the Senate might be saved.

Biden has the power to make this happen. As things stand, his debt relief plan is sabotaged by bad-faith litigation. While the president has rightly blasted the Republicans behind these lawsuits, the real story is more complicated. Biden could have directed the education secretary to cancel people’s debts using the “compromise and settlement” authority granted in the Higher Education Act of 1965, but instead his administration invoked a different and more limited legal authority. (It was this limited authority that the Texas judge formally took issue with.)

They also chose to make borrowers apply for the program, instead of automatically issuing cancellation – a slow-moving process that bought their billionaire-backed opponents valuable time to cook up legal arguments, find plaintiffs, and line their cases up with sympathetic, Trump-appointed judges poised to toe the conservative line.

The White House needs to learn from its mistakes and play hardball. Biden could knock the legs out from under these cynical lawsuits tomorrow by extinguishing all federal student loans immediately and permanently using compromise and settlement authority. Now that would generate some real “energy and enthusiasm” – the kind of energy and enthusiasm required to sustain and expand this week’s odds-defying electoral success.

This longer view is what motivates Nailah Summers, co-director of Dream Defenders, a group that just successfully mobilized young Floridians to elect Maxwell Frost, who will be Generation Z’s first member of Congress.

“Young people and Black folks in the US did what had to be done to keep the Democratic party from utter collapse in the midterms last night and it’s likely that the terrain in 2024 is going to be even harder,” Summers told me. “Crumbs and half measures won’t secure their place in the White House as life in the US gets harder. The party is going to have to take decisive action to make American lives better and they can start with canceling all remaining student loans.”

This month, young people held up their end of the bargain. Now Biden must honor his.

If Biden allows Republicans and billionaires to sabotage student debt cancellation without a fight, he risks breaking the fragile trust that has only just been built with younger voters. Student debt cancellation can be one of Biden’s signature victories, and a catalyst for a reinvigorated Democratic party, or a self-inflicted failure – an empty promise that risks demoralizing and demobilizing the demographic on which the future of the Democratic party, and arguably democracy itself, depends.

• Astra Taylor is a writer, organiser and documentary maker

• This article was amended 11 November 2022 to reflect legal developments shortly before publication