It’s worth reading Derek Thompson’s new piece in The Atlantic on the demographic movement of people within the United States and why the pattern is very bad news for the Republican Party. The overall story may be familiar to you but I guarantee that many of details will not be.

Before you check it out though, I want to acknowledge that people have been predicting for a long time that demographic change will eventually doom the conservative movement. That presumption is based on several assumptions that may or may not be accurate. If Latino immigrants, for example, behave more like their Irish and Italian predecessors than as a community of color, they may become more of a swing vote than a reliable part of the Democratic base. Generally speaking, however, younger generations are more diverse and progressive in their outlook than older ones, so time does seem to be on the Democrats’ side.

Thompson’s article comes at this from a different angle because it focuses less on who people are than on where they are choosing to live. This is important both for who controls Congress and for how the battle to win the Electoral College plays out.  Here’s are some interesting facts:

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.

You probably knew that the GOP has been hemorrhaging support in the suburbs, including in the South and Southwest. But the numbers are interesting for a second reason:

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.

It’s looking a lot like the Democrats are reaching parity in these three states. And they are not small states. With 38 Electoral College votes, Texas is the largest red state. Imagine if California suddenly became competitive for the Republicans and what that would mean for the Democratic Party. Georgia’s 16 votes match Michigan’s, making them interchangeable. And Arizona’s 11 votes match Indiana, Tennessee and Massachusetts. Collectively, they have 65 votes, which is more than California’s 55, and 12 percent of the total votes available. As a group, they get you almost a quarter of the way to the Oval Office.

What’s driving the change is largely an influx of younger voters who are moving away from heavily urban centers, particularly in the North and on the West Coast. They are bringing their culture and political sensibilities with them.

So, you can kind of set birthrate and immigrations pattern aside for the moment, even though those are big concerns for the white nationalists in Trump’s political base. What’s happening here is more related to the Democrats taking away the artificial advantage conservatives enjoy by virtue of having a wider distribution of votes than the Democrats. The left has lost two recent presidential elections despite winning the popular vote because their voters are packed into fewer states. But young people are moving from blue states to red states without a corresponding change in the other direction.

By itself, this would take a long time to turn states like Texas into battlegrounds, but Trump is accelerating the process by turning off well-educate suburban white voters and doing extraordinary poorly with almost all minority and immigrant groups. Only after we’ve gotten through these factors do we need to add in the influence of new arrivals to the country becoming voting citizens and having larger families.

It’s creating something of a perfect storm for the Republicans that they are hoping to offset by really maximizing their white working class and rural vote. That might work again, but it can only hold for so long.