Houston is not merely more Hispanic; the fastest-growing ethnic group is Asian. The kimchi taco is a hit. Some 90 languages are spoken. The city government will soon publish information in six languages. And 98 percent of the population growth in the first 10 years of this century has been nonwhite.

This diversity is rippling out to the far suburbs, counties that have long been white and Republican — and vital for winning statewide office. The most diverse part of the Houston region is now Missouri City, which straddles Brazoria County and Fort Bend County on the city’s southwestern edge and is filling with Hispanics, Asians and African-Americans seeking bigger homes and better schools.

The same trends are found in the Texas Triangle, an increasingly dense region bounded by Houston, San Antonio and Dallas-Fort Worth. It includes less than 20 percent of the state’s land but all its biggest cities. Conservative politicians do poorly in these settings.

The political shift is unmistakable. In Houston, 83 percent of residents favor a legal path to citizenship for undocumented immigrants. Six in 10 say abortion is morally wrong but oppose making it harder for women to get one. In August, an effort to repeal Houston’s new equal protection ordinance for gay, lesbian, bisexual and transsexual people failed.

Not only did Harris County vote for Barack Obama in 2008, but in 2012 it was joined by all of Texas’ big urban counties and cities, which Democrats have controlled for years. Republican strength is on the wane in some of those key suburbs, too. The Republican margin in Fort Bend County shrank in 2012 from double digits to just six points.

None of this is to say that Ms. Davis will win — but she might. And four years from now, she, or another candidate, will have an even easier time. No, that dusky sky up there is not blue. It is still burnt orange — but with quite a bit of purple.