When a 34-year-old democratic socialist defeats a political dynasty in the nation’s largest city, we’re witnessing more than another electoral upset.

Zohran Mamdani’s victory in New York reveals the collapse of the entire post-World War II political settlement that shaped Western democracies for three generations. The stable two-party systems, the broad catch-all coalitions, the predictable left-right oscillation, all of it is fragmenting. We’re watching the return of the fractious, multi-polar politics that characterised democracies before 1945.

The post-war period was the anomaly, not the norm. For seven decades, Western democracies enjoyed unusual stability built on expanding prosperity, rising home ownership, and intergenerational mobility that allowed major parties to construct enormous coalitions spanning classes and regions. That world is dead. Housing wealth is concentrated. Intergenerational mobility has reversed. The economic conditions that sustained catch-all parties have evaporated, and the party systems themselves are splintering.

What’s replacing it isn’t just political disagreement, it’s mutual contempt for the entire system. Gen Z’s structural collapse toward left populism is the most dramatic manifestation of this fragmentation, but it’s also occurring on the right side of politics as well.

However, conservatives who think they’ve found their answer in Trump and Reform UK are catastrophically misreading the landscape. Yes, right-wing populism has grown. But look where: outside big cities, in declining towns, among much older angry voters watching their world disappear. Trump and Reform succeeded by harvesting the rage of Boomers and older Gen X in urban and rural areas — places losing population and economic wealth.

It’s clear we are witnessing the rapid growth of two parallel but incompatible populist movements, separated by generation, geography, and fundamentally opposed worldviews but united by one thing: a burn-it-all-down mentality toward the establishment. In the UK, nearly half of 18-24 year olds are open to voting Green, whilst the same can be said for Boomers in Wheatley Hill moving to Reform. In Australia, Gen Z reports around 30 per cent support for the Greens across the entire country, irrespective of location, whilst One Nation surges at the expense of the Coalition in regional rural ageing Australia. Trump won by running up margins in rural counties with median ages above 45.

Neither movement wants to reform the system. Both want to overthrow it. This shared destructive impulse toward the post-war consensus is what makes the current moment so volatile and so reminiscent of the 1930s. The difference is what they want to build from the ashes.

These aren’t two sides of the same populist coin. They’re two incompatible visions competing for dominance in a fragmenting political landscape. But one will be around far longer than the other — simply because of the clear age disparity between them. The angry Boomers fuelling Trump and Reform can tear down the old order, but they won’t live to see what replaces it. Gen Z will.

Gen Z’s left-wing response to establishment failure is concentrated where the future is being built: in cities, in diverse communities, in places experiencing economic and population growth. Mamdani won New York City, the largest municipal economy in America. The Greens are becoming Labor’s main competitor in Australian seats with high youth populations and urban density. Labour’s losses to Greens in the UK came in gentrifying areas, not declining industrial towns.

Unlike the older voters Trump and Reform captured, Gen Z refuses to blame immigrants or minorities for their economic exclusion. They are the first truly post-national generation, digitally connected to the world, comfortable with diversity, and deeply sceptical of nationalist rhetoric. They identify that the landlord pricing them out of housing and the property developer sitting on land banks are local elites, not foreign workers. When conservatives try to redirect economic anxiety toward xenophobia, the playbook that worked brilliantly with older voters. Gen Z simply doesn’t buy it.

This explains the split in populist movements. Older voters in declining regions embraced economic nationalism fused with cultural backlash because their lived experience was of stable communities disrupted by change. Gen Z in growing cities experiences economic exclusion within diversity. Their problem isn’t cultural disruption but wealth concentration by their own established elite.

Both generations want to burn down the system that excluded them. They just disagree violently about who lit the match.

Mamdani’s victory exemplifies the emerging landscape. He defeated the entire establishment machine — Andrew Cuomo with his gubernatorial dynasty, Trump’s endorsement, Bloomberg’s backing, and millions in billionaire money. He won decisively with rent freezes, free buses, universal childcare, and higher taxes on the wealthy. Not moderate tweaks or means-tested programs, structural interventions acknowledging the scale of crisis. This is left populism: economically redistributive, unapologetically ambitious, explicitly framing politics as class power rather than technocratic management. And he did it in America’s largest city, becoming the first mayoral candidate to win over a million votes since the 1960s.

This is what the future looks like. Not Reform winning Clacton. Not Trump winning rural Pennsylvania. But democratic socialists winning cities where the economic and political power of the 21st century is concentrated.

The result is a fractured political landscape where old party brands command diminishing loyalty, where new movements rise rapidly, where coalitions are unstable and victories temporary. The Liberals losing Wentworth to the Teals. Labour losing Bristol to Greens. The collapse of traditional party vote shares across Western democracies. Minor parties and independents taking double-digit vote shares.

This is the new normal, or rather, the old normal, returned. The establishment parties stand helpless between two forces that both want them destroyed.

But here’s the warning for Australian Labor: they are not immune either. Centre-left parties that built post-war success on broad coalitions are being hollowed out from the left just as conservative parties collapse entirely. The Greens are already Labor’s primary competitor in youth-heavy urban electorates. When young people face a choice between incremental tinkering and structural transformation, they’re choosing transformation. Labor must offer radical solutions that convince a cynical generation they’re serious. Policy matching the scale of crisis. Not another means-tested scheme with Treasury-designed eligibility thresholds to minimise cost. The time for cautious incrementalism is over.

The post-war political order is dead. We’re entering an era where stable coalitions fragment, where new movements rise rapidly, where the urban-rural divide hardens into incompatible political cultures. Gen Z is building the future in cities with left populism, and they’re not interested in either establishment incrementalism or right-wing nationalism. Labor can either recognise this and transform accordingly, or join conservatives in celebrating yesterday’s victories while tomorrow burns down around them.

This is a version of an article previously published in the Financial Review.

The views expressed in this article may or may not reflect those of Pearls and Irritations.