Just hours after voting started in Texas, Kimberly Rubio cast her ballot in the same Uvalde city building where she waited in May to learn that her daughter, Lexi, was one of 19 fourth-graders fatally shot at Robb Elementary School. “If our children aren’t safe, neither are your jobs,” Rubio said as she walked out of her polling place with an “I voted” sticker. Nearby, another woman waved a “Don’t tread on me” flag. The deadliest classroom shooting in Texas history has cast a long shadow in the midterm elections, intensifying Republican Gov. Greg Abbott’s campaign against Democrat Beto O’Rourke and driving a blitz of television ads. On Thursday, a Republican congressman joined calls for Texas’ state police chief to resign, reflecting continued anger five months after the massacre. But with more than 1 million votes already cast in Texas, Uvalde families who have been most outspoken since the May 24 attack are facing an uphill climb for bigger shakeups on Election Day, including a change in governor. Abbott, who has waved off calls to tighten Texas gun laws since the shooting, has never trailed in polls. He is also seizing on national headwinds facing Democrats, who are in danger…