LONDON — Lara Spirit, an anti-Brexit organizer, was studying politics at the University of Cambridge in 2017, reading about the use of referendums as a way of settling political disputes. It was timely coursework: A year earlier, Britons had voted to leave the European Union.
But Ms. Spirit was growing alarmed at the omission of young people from the Brexit debate. Despite warnings in her readings about the risks of referendums, she delayed school and founded a group with other students to push for another public vote on Brexit.
They called it Our Future, Our Choice, and on Saturday it will be among a clutch of youth groups helping to lead an expected crowd of hundreds of thousands in a march on Parliament in support of a second referendum.
“We were sort of horrified that there hadn’t been a youth group that was a voice on the issue of Brexit,” Ms. Spirit, 22, said. “It will be my generation, of course, who will be making sense of this and dealing with the consequences of the decision we took in 2016.”
The fight for another public vote on Brexit, while still marginal among members of Parliament, has gained momentum among Britons, none more so than the young people steeling themselves for a lifetime of arguing about Europe.
They look around and see a bleak political landscape: Parliament is deadlocked; Prime Minister Theresa May is still pushing her unloved Brexit plan, even though it has been rejected by her putative allies in the Democratic Unionist Party of Northern Ireland; and the frightening prospect of a calamitous no-deal Brexit seems to be gaining more credibility every day.
But the way many young people see it, the political chaos and dysfunction are working in their favor, with the anti-Brexit forces gaining momentum.
By Friday, for example, more than four million people had put their names by Friday on a petition to revoke Article 50, the mechanism for leaving the European Union, and those numbers were growing.
As Saturday’s march approached, students in Bath and Bristol bought seats on a chartered train to London. Others are coming on buses. And in student union buildings across the country, young people this week were gathering to paint banners and persuade their classmates to join them.
Brexit has molded their politics as decisively as the Iraq War did an older generation’s. Worried about a chaotic British exit without an agreement with the European Union, students said they view a second referendum as the only way out of the current impasse and a crucial step to protect gains on climate change and workers’ rights.
“It’s awoken a group of people who otherwise might not have been engaged,” said Sally Patterson, 23, an officer at the University of Bristol Students’ Union. “If you have a mate from Greece who might not be able to continue studying next year, you’ve got a stake in their future.”
The timing of the march — only six days before the original date of Britain’s departure from the European Union — once seemed risky. Surely, it seemed, politicians would have settled the matter by then.
James McGrory, the executive director of People’s Vote, the umbrella group that is organizing the march on Parliament, said the group’s leaders were originally dubious about pouring money and energy into a rally in late March. But younger organizers prevailed on them to hold it anyway.
“It was me and senior colleagues who hemmed and hawed, ‘Should we do one or not?’” Mr. McGrory said. “The two things young people in the campaign said were, ‘You should have the courage of your convictions — do it.’ The other thing is they thought we could raise the money online to pay for it.”
The chances of a second referendum remain small. Labour Party leaders, who have long dithered over a second referendum, have never energetically backed the idea.
The most likely form it would take is a choice between the prime minister’s exit deal and remaining in the European Union. Many polls show that Britons have now gone from mostly thinking Britain was right to leave Europe after the 2016 referendum to mostly thinking the opposite.
And support for a public vote has grown, according to a mid-March poll by YouGov, with the option of staying in Europe favored over Mrs. May’s divorce deal or a no-deal exit.
With a following of hundreds of thousands of people on social media and email lists, Ms. Spirit’s group has invited young people to Parliament to petition their representatives and arranged for members of Parliament to visit schools to speak about Brexit. The group’s leaders have won big audiences on Twitter by posting video of encounters with pro-Brexit voters.
Along the way they have become valuable voices for an anti-Brexit movement that in 2016 was harmed by its association with the political class. (It was the Conservative prime minister at the time, David Cameron, who led the Remain campaign.)
“It’s more enjoyable to be the insurgents than the incumbents,” said Mr. McGrory, who is himself a veteran of the 2016 Remain campaign.
At Edge Hill University in northwest England, several dozen students were painting banners on Thursday in the students’ union bar. Among the anti-Brexit slogans: “Pulling Out Never Works.”
“It feels like an antithesis to the kind of bland politicians and political elite that are pushing Brexit,” Luke Myer, 24, vice president of the students’ union, said. “It’s real, and it’s irreverent as well. We like our memes and dumb slogans.”
Students said the atmosphere on campuses had seemed relatively dull in 2016, when the pro-Europe campaign stressed the potential economic problems if Britain left. Now, students are agitating about access to study abroad programs, research funding from Europe and the rights of their European classmates, said Shakira Martin, the president of the National Union of Students.
Many students, too young to vote in 2016, argue that so much time has passed since the first referendum that they deserve a fresh vote. In 2016, a majority of older voters favored leaving, while most younger voters wanted to remain. Demographic changes since then might alter the results of a second referendum, with more young people reaching voting age, students say.
However sparse the support for a second referendum in Parliament, the campaigners may succeed in laying the groundwork for fights in the months and years ahead for a closer relationship with Europe, said Rob Ford, a professor of politics at the University of Manchester.
Just as the Labour government of Tony Blair was blamed for Britain entering the Iraq War, he said, it will be Mrs. May’s government that will bear the stain from Brexit.
“If you’re a student, the whole first 10 years of your working life are likely to be impacted to a greater or lesser extent by this Brexit debate,” Mr. Ford said. “It’ll be seen as something Conservatives initiated and presided over.”