AUSTIN — A looming dogfight over “school choice,” fast emerging as a litmus test issue within the Texas GOP, has triggered a rush of huge campaign contributions in the run-up to the March primary. Most of the money is flowing to legislative candidates who favor voucherlike programs that proponents say will rescue some Texas families from ill-suited public schools – and to committees such as those controlled by Gov. Greg Abbott that are bent on defeating “school choice” opponents. Advertisement But Republican House lawmakers who oppose Abbott’s proposed education savings accounts as a potentially budget-busting entitlement are receiving some financial...