As noted above, migration isn’t the only reason southern metros might be shifting to the Democratic Party: Longtime residents may be switching parties in response to Trump, for instance. Republicans have likely hurt themselves by moving further to the right to galvanize their white exurban and rural base, even as their support has thinned in the suburbs and among working-class white women.

But domestic migration is key. Just look at Texas. CNN exit polls for its 2018 Senate election showed that Beto O’Rourke was buoyed by recent movers, winning more than 60 percent of those who had moved to Texas within the past 10 years. At current migration rates, the “Texas Five” counties could easily add another 200,000 votes between 2016 and 2020, putting more pressure on Trump’s margin in the state. A September poll conducted by Univision and the University of Houston found the top six Democratic presidential contenders all leading Trump in Texas.

Outside of national elections, the blue flood of the sunbelt could have other political implications, like more showdowns between blue cities and red states. As The Atlantic’s David Graham has argued, North Carolina’s GOP-led general assembly has waged war against liberal cities like Charlotte, for instance by reversing a local ordinance that banned discrimination against LGBT people. This sort of state-city showdown could become a regular feature of southern politics. In the last six months, both the Dallas Morning News and the Dallas Observer have run features bemoaning the Californication of northern Texas, with the former noting that “conservatives fear these domestic migrants will bring with them a liberal ideology that would disturb the Texas way of living.”