WASHINGTON — “I am a classically trained engineer,” says Rep. Will Hurd, a Texas Republican, “and I firmly believe in regression to the mean.” Applying a concept from statistics to the randomness of today’s politics is problematic. In any case, Hurd, 42, is not waiting for the regression of our politics from the extreme ends of the ideological spectrum to something like temperate normality. He is leaving Congress at the end of this, his third term. And he sees portents that his blinkered party would be prudent to notice.

Hurd is one of six Texas Republican congressmen who has decided not to seek reelection next year. Until this year, none of them had, since 2011, experienced the purgatory of being in the House minority. In the 2018 “Texodus,” five Texas Republican representatives retired (a sixth resigned) and two were defeated. Of the 241 Republicans in the House when Donald Trump was inaugurated, almost 40% are gone or going. See a trend?

Hurd, who is not foreswearing public life, insists, “I’m just getting started.” Might he come back to electoral politics? “For sure.” His “passion” is “the nexus between technology and national security.” He is, however, saying goodbye to the rigors of the “DC to DQ” tours that have regularly taken him to the far reaches of his district. For you effete coastal residents who are unfamiliar with the delights of flyover country, DQ means Dairy Queen. Hurd meets gatherings of constituents at DQs because “every town has one and everyone knows where they are.”

In 2018, he was one of just three Republicans to win a district carried by Hillary Clinton. (She won his by 3 points.) His House race was the nation’s fourth-most competitive: He won by 926 votes. But, then, his largest victory, in 2016, was by just 3,051 votes. His district, which includes 23% of Texas’ land and extends from San Antonio’s fringe to New Mexico’s border, is the state’s largest, encompassing all or parts of 29 counties and 820 miles of the U.S.-Mexico border. It is 58,000 square miles — almost as big as Georgia and larger than Illinois and 25 other states. It is 69% Hispanic and just 4% African American.

Hurd, an articulate, assertive 6’4” former CIA operative, and the only African American Republican in the House, thinks voting trends “are moving so fast” that 2020 “has nothing to do with 2016.” Just as “U.S. economic and military dominance are no longer guaranteed,” neither is Republican dominance in Texas, a state that is hardly immune to national trends.

In the 2016 U.S House of Representatives elections, no Republican incumbent from Texas lost and only one was elected with less than 55%. In 2018, two lost and 10 received less than 55%. In 2016, four incumbent Republicans in Texas’ House were defeated and only four won with majorities under 55%. In 2018, there were eight loses and 16 won with less than 55%. John Cornyn, who recently stepped down as the second-highest Republican leader (majority whip) in the U.S. Senate, has won three terms with majorities of 55.3%, 54.8% and 61.6% but seems headed for a more competitive race next year. No wonder Rep. Cheri Bustos of Illinois, chair of the Democratic Congressional Campaign Committee, says Texas is “ground zero” for Democratic attempts to strengthen their hold on the House.

Nationally, Republicans are decreasingly strong where two generations ago they were especially robust — in suburbs. Texas ranks high among the states in terms of the percentage of the population that is suburban. And statewide, whites are a minority.

In 2008, with the Great Recession under way, John McCain carried Texas by 12 points. In 2012, Mitt Romney carried it by 16. In 2016, Trump (who Hurd did not endorse) won by nine points. In Texas’ most important 2018 contest for a federal office, incumbent Republican Sen. Ted Cruz won by just three. See a trend?

If the Democratic Party can collect Texas’ electoral votes — 38 today, perhaps 41 after the 2020 census — as well as California’s 55, it will reap 35.5% of a winning 270 from just two states. Then the GOP will have almost no plausible path to 270, and Democrats who are currently hot to abolish the Electoral College will suddenly say: Oh, never mind.

And Hurd will repeat what he says today: Texas is “already purple.” Republicans “have to get out of our own way” because “if the Republican Party in Texas does not start looking like Texas there will not be a Republican Party in Texas.”

— Will’s email address is georgewill@washpost.com.