2020 trend: Big cities keep getting bigger

(CNN)We are increasingly a country of cities. Big cities.

There are now 775 cities in America that have a population of more than 50,000 -- and, collectively, 127 million people live in those cities, according to estimates from the US Census Bureau released Thursday. That's nearly 40% of the total population in the country. And since 2010, the populations of those big cities (50,000 and above) has risen, on average, by almost 12,000 residents.
The growth, particularly of late, has come from cities in the South and West. "Among the 15 cities or towns with the largest numeric gains between 2017 and 2018, eight were in the South, six were in the West, and one was in the Midwest," according to the Census Bureau release. Phoenix, Arizona, led that list -- adding more than 25,000 residents in a single year. Two Texas cities -- San Antonio (almost 21,000 new residents) and Fort Worth (19,552 new residents) were second and third on the list.
Why does this matter, politically speaking? For lots of reasons!
    1) The national vote has been trending away from rural areas and toward urban and suburban areas for more than a decade now. In 2004, 30% of voters were in urban areas, 46% in suburban areas and 25% in rural areas. In 2016, it was 34% urban, 49% suburban and just 17% rural. Those trends should boost Democrats. In 2016, Hillary Clinton beat Donald Trump 60% to 34% in urban areas; in 2004, John Kerry won urban areas over George W. Bush by 9 points.
    2) The South and West will get more and more powerful in Congress and picking a president. Estimates based on population growth through 2018 show seven states projected to gain congressional seats (and, therefore, electoral votes) after the next Census: Arizona, Colorado, Florida, Montana, North Carolina, Oregon and Texas. Texas is projected to gain three (!) new congressional seats -- taking its delegation to 39 -- while Florida is set to gain two new House districts. (The states expected to lose seats? A large cluster in the Midwest and East, including Illinois, Ohio, Pennsylvania, New York, Michigan and Minnesota.)
    3) Our two parties increasingly represent totally different Americas. As Ron Brownstein wrote in the wake of the 2018 midterm election: "The result is a widening trench between the parties in the House that encapsulates the growing distance between a Democratic coalition centered on minorities, Millennials and college-educated white voters, most of them clustered in urban areas, and a competing GOP coalition that revolves around evangelical, rural and blue-collar whites who often live beyond it."
      The Point: Demographics, as they say, are destiny. While Trump's 2016 victory proved that predictions of demographic doom for Republicans were overstated, these ongoing growth (and decline) trends suggest Republicans will need to find a way to better appeal to urban voters, or run the long-term risk of shrinking as a national party.
      CORRECTION: This story has been corrected to show 49% of voters came from suburban areas in 2016.