So just imagine what would happen to the American political picture if more Democrats moved out of their excessively liberal enclaves to redistribute themselves more evenly across the vast expanse of Red America?

Or don’t imagine. Just … wait.

Derek Thompson: How Democrats conquered the city

Two weeks ago, I published an article on what I called the urban exodus. More specifically, it is a blue urban exodus, as left-leaning metros in blue states are losing population. The New York City metro area is shrinking by 277 people every day. Other areas bleeding thousands of net movers each year include Los Angeles, San Francisco, San Jose, San Diego, Chicago, Boston, and Baltimore—all in states that routinely vote for Democrats by wide margins.

These movers are U-Hauling to ruddier states in the South and West. The five fastest-growing metros of the past few years—Dallas, Phoenix, Houston, Atlanta, and Orlando, Florida—are in states won by Trump. The other metro areas with a population of at least 1 million that grew by at least 1.5 percent last year were Las Vegas; Austin, Texas; Orlando, Florida; Raleigh, North Carolina; Jacksonville, Florida; Charlotte, North Carolina; San Antonio; Tampa, Florida; and Nashville, Tennessee. All of those metros are in red or purple states.

It’s not just liberals moving to the South. After all, movers to Florida are often retirees who fit squarely in the Fox News demo, and some of the people moving from California to Texas are conservatives. But today’s domestic migrants are often college graduates of the exceedingly liberal Generations Y and Z. “The current migration to these suburbs is mostly people in their 20s and 30s, or Millennials, who are more diverse and liberal than the rest of the population,” said William Frey, a demographer at the Brookings Institution. According to his research, Americans ages 20 to 40 are three times as likely to move as people ages 50 to 70.

This drip-drip-drip of young residents trickling down into red-state suburbs is helping to turn southern metros into Democratic strongholds. (Of course, migration isn’t the only factor pushing these metros leftward, but more on that later.) In Texas, Democrats’ advantage in the five counties representing Houston, Dallas–Fort Worth, San Antonio, and Austin (the “Texas Five” in the graph below) grew from 130,000 in the 2012 presidential election to nearly 800,000 in the 2018 Senate election.

In Arizona, from 2012 to 2016, Democrats narrowed their deficit in Maricopa County, which includes Phoenix, by 100,000 votes. Two years later, in the 2018 Senate election, the county swung Democratic, with Democrats gaining another 100,000 net votes.

In Georgia, from the 2012 presidential election to the 2018 gubernatorial elections, the four counties constituting most of Atlanta and its suburbs—Fulton, DeKalb, Cobb, and Gwinnett—increased their Democratic margin by more than 250,000.

What’s remarkable about these changes isn’t just their size, but their resemblance to Trump’s 2016 margins. Trump won Texas in 2016 by 800,000 votes. He won Arizona by 90,000 votes. He won Georgia by 170,000 votes. If these states’ biggest metros continue to move left at the same rate, there is every reason to believe that Texas, Arizona, and Georgia could be toss-ups quite soon.