Bellwether counties barely exist in midterms

A bellwether county is one that moves the way the nation moves. In U.S. House midterms, there are very few of them. Across five pairs of midterms from 2002 to 2022, only 13% to 16% of counties swung in the same direction as the national House vote and landed within 4 points of it, except in 2022, when 33% to 38% did. Counties with a perfect record so far were barely more likely to pass the next time: 0 to 4 points, where the groups are large enough to measure.

What it means

Direction is easy in a wave year; size is hard. In 2006, 2010 and 2022, between 80% and 91% of counties moved the same way as the nation. Far fewer moved by about the same amount. County House swings depend on candidates, incumbents and open seats, which the national vote averages away.

Midterm counties are noisier than presidential ones. In presidential elections, 19% to 66% of counties pass the same test each cycle. In midterms, the pass rate is 13% to 16% in every cycle except 2022.

A past record predicts little. In the 2010–2022 panel, which has the largest groups, counties that had passed every swing so far did 0.6 and 3.5 points better on the next one than counties that had already failed. In the contested-only sample the edge was 0.3 and 1.4 points.

The handful of perfect counties look like luck. Two counties passed all five swings from 2002 to 2022: Brevard, Florida and Spokane, Washington. That is more than chance would give, but in the larger 2010–2022 panel, 18 counties passed every swing against 15.7 expected by chance.

What it doesn’t mean

It does not mean counties tell you nothing. They are useful for seeing where a swing is coming from. 2018 is the example: the nation moved 14.3 points toward Democrats, but only 59% of counties did. Weighted by votes, 83% moved toward Democrats. The 2018 wave came from large and suburban counties.

It does not apply to every office. Governor results track their own state more closely: in most pairs of consecutive midterms, 77% to 85% of counties moved the same way as their state, and a perfect record so far gave a 4 to 14 point edge, slightly better than House races.

It does not say 2026 will be like 2022. The 2022 pass rate was high because 91% of counties moved toward Republicans, many by similar amounts. That is one cycle, not a trend.

How we checked

We built county results for U.S. House, Senate and Governor for every midterm from 2002 to 2022 from free precinct and county returns. Our national House vote is within 0.3 points of the published figures for 2006 to 2022. Coverage is thin in 2002 (56% of counties), so some tests start in 2006 or 2010.

A county’s House margin sums every district that touches it. The swing test asks whether a county moved in the same direction as the national House swing and within 4 points of it. We ran it on all counties and on a contested-only sample that drops counties with uncontested districts or suspect totals.

For the survivorship test we compared counties with a perfect record so far against those that had already failed, and checked counts against a shuffle of 2,000 random reorderings.