I don’t think there was a lot of realignment in state house control in 2020,
Historically state houses have changed quite a bit, at least in the last 20 years. Under Bush the democrats steadily gained control of state houses, and under Obama the GOP gained control of statehouses (fairly quickly in 2010, because democratic turnout was low that year).
But I don’t think there were a lot of statehouses picked up in 2020. And in 2018, democrats only picked up 6 state houses. Considering that there are 99 statehouses, those are low numbers.
The graph below has what state legislatures (both house and senate) were under one party control or split between the two parties. Tons of gains for the democrats under Bush, tons of gains for the GOP under Trump. But the changes seem to have been minor in 2018 and 2020.
So any idea why state houses aren’t switching as much? is it gerrymandering, or just high turnout among republican voters since 2018 and 2020 were democratic years?
Ticket-splitting has declined, which means it’s harder for local candidates to run very far ahead of (or behind) the national parties’ popularity in their area. Gerrymandering certainly affects this, but the increase in partisan polarization means most states just aren’t competitive enough for it to matter except at the margins. Like, Democrats controlled the Oklahoma House of Representatives until 2004, despite having lost every presidential election there since LBJ won it in 1964; that kind of thing isn’t happening any more.
Another factor is that we continue to sort ourselves geographically by politics. Democrats are increasingly urban and Republicans are increasingly rural. Since states very quite a lot in population, you’re going to see that as a trend toward Republican control if you graph # of state legislatures by party.