When Prime Minister Boris Johnson called a December general election last month, Johnny Maclean, a 19-year-old fashion student, was delighted. Too young to vote in the 2016 European Union referendum, but ardently anti-Brexit, he would finally have his say.

After reading the policy platforms of the main opposition parties, Mr. Maclean concluded that the Labour Party offered the best opportunities for young people.

“They are promising the largest youth investment out of any other major U.K. party,” he said in a recent interview. “They are promising the full scrapping of tuition fees, free bus travel for all under 25s, raise the minimum wage to £10 and mass invest into youth services to reverse and go beyond the one billion cuts in youth services by the Tories.”

While young voters tend to favor the Labour Party, the youth vote shows the same tendency toward fragmentation as the wider British left. Many have shifted to the Liberal Democrats, a more centrist party with an adamantly anti-Brexit stance, and the Greens.

James Sloam, the author of “Youthquake 2017: The Rise of Young Cosmopolitans in Britain,” believes that youth turnout will be high this week. “All the evidence shows that if you vote in your first election it becomes a habit, so young voters from 2017 would be likely to vote again as well as first-time voters,” he said.

Dr. Sloam’s research found that in the aftermath of the global financial crisis in 2008 young people, having borne the brunt of austerity, unemployment and cuts to services, have become more politically engaged.