The newcomers are so numerous that at monthly meetings of the Sun City Republican Club, President Cathy Cody puts a placard at the front of the room with the text of the Texas Pledge: "Honor the Texas flag; I pledge allegiance to thee, Texas, one state under God, one and indivisible."
The pledge is a legacy of the state's former status as an independent nation that's recited in every school room and civic gathering across Texas, but is unfamiliar to many new residents.
About 40% of Texans were born somewhere else: 22% from other states and 18% outside the U.S. And three deeply Democratic states account for 62% of the net domestic migration to Texas, according to IRS statistics: California, New York and Illinois.
The migrant wave hasn't been uniformly liberal, however. Among the Californians in particular there's a segment moving to Texas "who are getting the hell out" to escape rising tax burdens, Large said. And Texas's large number of military bases means that military families -- who typically lean Republican -- constitute much of its migration.
Local Republicans aren't the only ones worried about losing their grasp on Texas. Brian Walsh, president of the Trump-endorsed super PAC America First Action, is too.
Rattling off a list of battleground states the super PAC will spend money in next year, Walsh put Texas in its own special category: the "watch list." He's assuming it goes for Trump, but not without looking over his shoulder.
"You got to keep an eye on Texas," he said.
Trump won Texas by 9 percentage points in 2016 and maintains a 70% approval among Texas Republicans. But there have been tremors across Texas politics since then.
O'Rourke came within 215,000 votes of knocking off Cruz in 2018, in a contest that made national headlines and attracted millions of dollars in outside donations. Had he won, he would have been the first Democrat to hold a Texas statewide office in more than 20 years.
Since losing the majority in the House of Representatives in November, five Republican congressmen from the state have announced their retirements at the end of this Congress.