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The Upside of Polarization?

A mix of factors has loosened the hold of the “median voter theorem” on American electoral politics. But out-of-touch extremism by one party still offers opportunities for others to build broad coalitions, winning not just the middle but the majority.

CAMBRIDGE – While there are no ironclad laws of politics, two tendencies in the United States – midterm swings against the incumbent party (the “midterm blues”) and the negative electoral effects of inflation and unemployment (“political business cycles”) – come pretty close. US President Joe Biden (whose approval rating has sunk for the past year) and the Democrats should not be surprised if they suffer a massive rout in the 2022 midterm elections.

But other long-accepted political truths have been discarded. For decades after World War II, two-party competition within a majoritarian system was thought to have a moderating effect. According to the celebrated “median voter theorem,” originally proposed by the economist Duncan Black and then later by the political scientist Anthony Downs, if one party veered too far from the center, it would pay for it at the polls.

Imagine that the US electorate has a range of views about the appropriate level of the federal minimum wage. Some on the right think there should be no federal minimum wage at all, whereas some on the left think it should be at least $18 per hour. Now suppose that the “median” of this distribution of voters points to a preferred minimum wage of $12 per hour (the rate above and below which half the electorate falls).

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