As some see it, the Texas Republican primary for U.S. Senate is a battle for the future of the party: Longtime incumbent John Cornyn represents the conservative establishment, while Attorney General Ken Paxton is a rising MAGA firebrand. After Tuesday’s election, that battle will continue, as neither candidate broke 50 percent, and therefore they will face each other in a runoff in May. While Cornyn is a staunch fossil fuel ally—no one would mistake him for an environmentalist—Paxton has gone a...