The year 2008 changed more than the economy. While Wall Street collapsed and a new president took office, something subtler was happening to the American public—they were pulling apart. Not gradually, not uniformly, but in a sharp, sustained divergence that would define the next dozen years of US politics.
Lee de-Wit at the University of Cambridge’s Political Psychology Lab has watched this split unfold through 35,000 survey responses spanning nearly four decades. “Our study shows that 2008 was a major turning point for the divisions between left and right on many of the issues that define contemporary US politics,” he says. Before that inflection point, from the late 1980s through the mid-2000s, American divisions essentially flatlined. Then came the shift.
What’s driving the division turns out to be asymmetric—and counterintuitive. “Although sentiment varies by topic, the American public has moved left on many issues during the 21st century,” says de-Wit. “This shift may surprise those familiar with the rightward turn of Republican leaders over the same period, as well as recent US headlines.” The left-leaning cluster in the US population has moved 31.5 per cent more liberal since 1988. The right-leaning cluster? Just 2.8 per cent more conservative.
This creates an odd dynamic. “Right‑leaning Americans have remained fairly stable in their positions for the last 35 years, and may feel left behind as half the country has shifted towards an ever more progressive outlook on many issues,” de-Wit explains. Part of the recent success of the US right, he suggests, may be their ability to tap into outgroup animosity for a perceived “woke” left, rather than firm belief in extreme positions.
The Cambridge team used machine learning algorithms to sidestep a problem that’s plagued polarization research for years—the question of self-identification. When you measure division between Democrats and Republicans, are you measuring genuine disagreement, or just people getting better at choosing the right label? David Young, who led the analysis, puts it bluntly: “There can be various reasons why voters feel they belong in a particular party, from media they consume to communities in which they live, even if many of their attitudes don’t fit.”
So instead of relying on party labels, the researchers used clustering algorithms—computational techniques that sort people into groups based purely on their policy positions across 14 issues, from abortion to economic equality. It’s a bottom-up approach. The algorithm doesn’t know or care about party affiliation; it’s simply looking for coherent clusters of similar viewpoints.
What they found was both sorting and polarization happening simultaneously. Between 1988 and 2024, 20 per cent more people in the left-leaning cluster now identify as Democrats, and 51 per cent more call themselves liberals. On the right, 30 per cent more identify as Republicans, 39 per cent more as conservatives. “Using machine learning, we can see that both are happening,” says de-Wit. “People are sorting themselves more using political labels, alongside a genuine increase in polarization on the core issues.”
But there’s something else happening—what Young calls pluralistic collapse. “In the past, someone with left-wing views on one issue might have held right-wing views on another. That’s rarer now.” The issues that showed the biggest shifts? Abortion rights and traditional family values, where a late-1980s consensus has given way to sharp division. “I think this consolidation happens as people pick up clear cues from political elites about what goes together,” Young says. “It makes average positions more extreme, and widens gaps between US citizens.”
The 2024 data offers a tentative hint that this period of increasing polarization may be levelling off, though it remains far higher than previous decades. De-Wit is careful about overinterpreting. “Political groups have moved further apart in recent years, but these divisions are still fuzzy, and Americans are not split into entirely opposing tribes when it comes to the issues.”
What makes the US unusual, according to the team’s global analysis of 57 countries, is that its political clusters have stayed the same size. In developing countries, there’s typically a large culturally conservative majority and a small liberal minority. In highly developed countries, liberal views tend to dominate, if narrowly. “The United States is unusual in having a left and a right of roughly equal size,” says Young. “This has been the case for a long time, and it may help explain why polarization in the US feels so intense.”
The equal-but-opposite structure might make 2008’s divergence particularly potent. Two halves of the country, moving in different directions at different speeds, with neither gaining numerical advantage. The stalemate persists, but the centre ground keeps shrinking.
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