The Democrats have not controlled all 8 Senate seats in the Southwest states of AZ, CO, NM and NV since 1941. And the Democrats have not carried all four of these states in a Presidential election since 1948. This year, the Democrats could quite plausibly accomplish both of these feats--something the Democrats have not accomplished together since 1936. Ron Brownstein makes the case here, a case which accords with my own reading of the polls and trends and, at the Presidential level, is consistent with the data rolling in from the massive Nationscape survey. I'll have more to say about this down the line.
And then there's this:
"The scariest prospect for Republicans is that everything said ...about Arizona and Colorado in particular could also apply to Texas, the foundation stone of the GOP's national political strength. From Dallas/Fort Worth and Austin down south through Houston and San Antonio, the four metropolitan areas in what's called the Texas triangle account for just over two-thirds of the state's votes and jobs and more than three-fourths of its economic output.
All of them rank among America's 10 fastest-growing cities, according to the census. (All are also big recipients of transplants from California, which sent over 86,000 migrants to Texas just in 2018.) And as they grow, they are shading more blue: In his narrow 2018 defeat, the Democratic Senate candidate Beto O'Rourke won the five counties encompassing those cities by nearly 800,000 votes, roughly six times then-President Barack Obama's combined margin just six years earlier.
Like other observers, [Brookings Mountain West head Robert] Lang says that for now, the massive GOP advantage in Texas' rural areas should allow Trump to hold it in 2020 (albeit likely by a much smaller margin than his 9-percentage-point victory last time). Republican Sen. John Cornyn also looks tough to beat. But in both parties, many agree that the shift away from the GOP in the large metropolitan areas driving the state's population growth have placed Texas on the same political moving walkway as Colorado, Nevada and Arizona, only a few steps behind."
For what it's worth, the Nationscape data since the beginning of the year has Trump only up by a single point in Texas!