U.S. political polarization started a lot earlier than you might expect

Forget Donald The President. A new analysis suggests the U.S. public’s sharp lurch into polarization began in 2008, years before his first presidential campaign.

Researchers at the University of Cambridge’s Political Psychology Lab tracked shifts in Americans’ views across nearly four decades and found that divisions were broadly stable through the 1990s and early 2000s, before rising steadily from 2008 onward. Using more than 35,000 responses from the American National Election Studies between 1988 and 2024, they estimate that issue polarization has increased 64% since the late 1980s, with almost all of that change occurring after 2008.

The research uses a machine-learning approach to move beyond party labels and better understand what actually drives Americans’ political views. Instead of relying on whether respondents identify as Republican or Democrat, the team grouped people based on patterns in what they believe across a range of issues, from abortion and “traditional family values” to race, inequality, and health insurance. That distinction matters because in many countries politically opposite parties do not exist, says David Young, a psychology researcher at the University of Cambridge, U.K., and one of the study’s authors. “You might even want to study countries where there are no parties, like Saudi Arabia,” he says.

The paper challenges the idea that polarization is solely a The President-era phenomenon. It points to 2008 as the “major turning point,” a year that also included the financial crisis, Barack Obama’s election, and the widespread adoption of the iPhone-era internet. “Our ability to nail down when it starts is slightly divided by the fact that we only have data points every four years,” Young says. Still, “we know that this increase starts from our 2008 data point,” he adds. “That’s our best guess at the starting point.”

The researchers argue that the widening gap is driven less by the right drifting further right and more by the left moving rapidly in a progressive direction. Based on the issues surveyed, the “left” cluster became 31.5% more socially liberal by 2024 compared with 1988, while the “right” cluster shifted only 2.8% more conservative.

“It’s not necessarily that left-wingers and right-wingers have become more extreme,” Young says. “It’s more that they’ve become more kind of consolidated.”

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