Between 2010 and 2018, the 27 counties that comprise these major metropolitan areas collectively added nearly three million people — an increase of 19 percent — and today they make up one of the most vibrant economic areas in the entire country. Republican elected officials have bragged about the state’s ability to attract new businesses, but the added growth has helped to change the political balance in the state.

One change is the increased dominance of the big cities and suburbs in overall turnout. According to data compiled by Richard Murray and Renee Cross of the University of Houston, the 27 counties that make up the major metropolitan areas account for 69 percent of the statewide vote, compared with 60 percent in 1996 and 52 percent in 1968.

For a long time, the balance between metro and nonmetro Texas didn’t make much difference. The metropolitan areas split their votes between Republicans and Democrats in about the same proportions as in the smaller towns and rural areas, according to Murray and Cross. That began to change in the past two decades and has quickened in the past five years. Not only do the big cities and surrounding suburbs account for a larger proportion of the statewide vote, they are increasingly voting Democratic.