California’s population growth has slowed notably in the last few years amid a surge of people leaving the state for other parts of the country. The state’s high cost of living is a key driver of this out-migration. Lower-income Californians are more likely to move, and housing costs have become a much more common explanation for moving—even as jobs and family remain important factors as well. But these are not the only considerations. Partisanship now shapes the state’s migration too, with those moving out of the state more likely to be Republican and those moving in more likely to be Democratic.

There are lots of reasons to think that Republicans and conservatives would be more likely to leave California. Democrats dominate the state’s governing institutions and have passed relatively liberal policies. In PPIC surveys, California Republicans tend to disapprove of statewide elected officials, and they are far more likely to say they have thought about leaving California. In addition, Republican registrants have disproportionately fallen off the state’s registration records over time in a way consistent with more Republicans leaving California. But this evidence is all from current Californians. It does not capture those who actually made the move to someplace else and contains no information about where new arrivals came from.

To address this issue, we turn to registration data for all 50 states. Although this source does not include all movers, it includes those who were registered in their origin and destination states and filed a change of address form with the postal service.

According to the data, voters who moved out of California between the 2020 and 2024 presidential elections have a strong Republican lean. Recent departures (39%) are much more likely to be Republican compared to California registrants overall (25%). By contrast, those who moved into California during that period are disproportionately Democratic (54%, compared to 45% of Californians overall). The shares of no party preference and minor party registrants are more similar among those moving in (28%), those moving out (26%), and Californians overall (30%).

Because more registrants have moved out than in during this period, the net flow is even more Republican than these numbers suggest. Between these two elections, almost five times as many Republicans in the data have moved out of California than have moved in. The same ratios for Democrats (1.5) and no party preference/other parties (2.1) suggest real net losses to other states, but at far smaller rates.

Though migration out of California leans Republican overall, the destination state matters. Californians leaving for Republican states are much more likely to be Republican than Democratic, compared to Californians as a whole, while those leaving for Democratic states are more likely to be Democratic than Republican. This partisan sorting is strong enough that it makes the Republican destination states even more Republican—and the Democratic states more Democratic—than they already are.

There are some exceptions. For example, while California migrants to Ohio and Wisconsin are marginally more Republican than Californians overall, they are actually somewhat more Democratic than registrants of their new home states. But, on the whole, people leaving California go to states aligned with their partisan affiliation.

As some Californians leave for states with fellow partisans, the same is happening in reverse among those coming to California. New arrivals are more Democratic than Californians as a whole, almost regardless of the state they came from. And they are more Democratic than the states they left in every case but one (Hawaii, one of the most heavily Democratic states in the country).

California is part of a larger process that appears to be slowly polarizing the country’s geography. This process makes California more Democratic than it would otherwise be, as Republicans leave for other states and Democrats move in.

All the same, migration is only one way to change the state’s politics. Between the 2020 and 2024 presidential elections, the young people who became eligible to vote for the first time registered Republican at a much lower rate (18%) than the state overall (25%) and chose smaller parties or no party preference at a much higher rate (40% vs. 30% for the state overall). Nor do all signs point Democratic. In the midst of these trends that have shifted the state to the left, California voters in 2024 voted more Republican than in any presidential election in 20 years.

So this migration pattern does not necessarily produce an inevitable political result. But it does suggest a shift in the perspective of the people living in California that may shape future politics. Given that the size of overall migration flows in and especially out of the state are large, the impact of this pattern will build over time if it continues. Coupled with trends among new young registrants, it will make it easier for Democrats’ dominance in statewide politics to continue.