How is domestic migration reshaping politics in Republican counties?
Core argument: Domestic migration has historically added about 0.5% a year to the population of reliably Republican counties while subtracting 0.6% a year from reliably Democratic ones.
Our number crunching shows that domestic migration has historically boosted the population of reliably Republican counties by about 0.5% a year, while reliably Democratic ones have lost 0.6%. The opposite is true of international migration, which has historically added 0.5% a year to solid-blue counties, compared with just 0.1% in solid-red ones. Data from the IRS show that the fastest-growing red counties draw an unusually large share of newcomers from politically unfriendly territory. In 2022-23 more than 20% came from solid-blue places and around 40% from competitive ones. This may already be affecting voting patterns. Before 2016, fast-growing red counties leaned more Republican than slower-growing ones. That has now flipped: slower-growing red counties lean more Republican, and GOP support in faster-growing ones has weakened.

