I'm the slightly odd duck here when it comes to unions and unionization. I'm neither against or for a union without knowing the particular facts of a situation. More directly, I am of the opinion that unionization is usually the result of poor management practices (unfair wages, unsafe working environment, ignoring employees).
First, the UAW and unions in general haven't been able to grasp that times have changed. It isn't likely that the worker are going to want a closed shop. It isn't likely that they are going to accept certification as permanent fixture which means the union being subject to re-certification or decertification votes every few years. In other words, unions are going to have to sell their services to their desired customers. That is going to mean things like lowering their process and actually efficiently representing the workers rather than behaving as slush funds for corrupt politicians and organized crime.
Second, the union is approaching the wrong workers. Employees at the car company vehicle assembly plants report that they are fairly happy with their condition. They feel they are paid fairly, their work is generally safe, and that management generally listens to their input. That isn't fertile ground for a union. Where they should be focusing their efforts is at the plants where the parts for the assembly plants are being built. There are repeated reports, including Federal OSHA complaints and fines, that the employees are not fairly paid, the working conditions are dangerous, and management does not care about employee concerns. There isn't as much money to be made there, but if UAW wants to show the average Alabamian or Mississippian that they can provide them some positive worth, they really should start at those places.