“If Democrats can make that pivot, they are in the driver’s seat for a long time to come, because these Sun Belt states are the growing states,” William Frey, a demographer at the Brookings Institution, told me.

The challenge facing Democrats is that while the demographic trends are more favorable for them in the Sun Belt, the political attitudes among the white population specifically are not. This could expose the party to the same risk in 2020 that I wrote about on Election Day 2016: that the Democrats’ old coalition in the Rust Belt will crumble faster than its new coalition coalesces in the Sun Belt. If that happens, it could leave Democrats just short in enough key states in both regions to allow Trump to win reelection, even if he loses the total popular vote by a greater margin than he did last time.

Read: Democrats’ two roads to beating Trump

While Democrats posted significant gains in both areas in the 2018 elections, in many ways their Sun Belt victories were more striking because they showed the party improving in places it had not successfully competed in before, including the suburbs of Atlanta, Houston, Dallas, and Phoenix. Some strategists are now warning that the Democrats’ intense focus on Michigan, Wisconsin, and Pennsylvania shouldn’t distract them from efforts to advance from those Sun Belt beachheads in 2020. They’re especially concerned because the results of state legislative races in the region will determine redistricting processes, which will shape the political competition in those states for the next decade.

“It’s hard not to be obsessed with the three states that tipped the election to Donald Trump, but it’s also easy to be fighting the last war,” says Vicky Hausman, a co-founder of Forward Majority, a group working to elect Democrats to state seats. “I think our job right now is to sound the alarm that there is insufficient attention and focus and investment, particularly at the legislative level … in these Sun Belt states. And Democrats around the country have a clear interest in making smart investments there.”

The continued growth of the Sun Belt is the biggest takeaway from the new population estimates that the Census Bureau released in late December. They were the last before the 2020 decennial census, which will be used to reapportion both congressional seats and Electoral College votes among the states.

Using these estimates, Kimball Brace, the president of the nonpartisan political-data firm Election Data Services, has calculated that seven states are on track to gain House seats and Electoral College votes, while 10 are in position to lose them. (New distributions would first affect the 2022 midterm elections and later the 2024 presidential contest.) The states that voted for Trump in 2016 would make a net gain of three Electoral College votes, while the states that voted for Hillary Clinton would lose three, a modest partisan shift in all.