You can't. Did you lose anything? Did one spoofed message have any bearing on the result?
Maybe if people came together it would be different, but whoever made the decision could say that they knew these messages were off and had no effect on the result.
Who would you sue?
I am not a lawyer, but I thought in cases like this you can sue a “John Doe” and then ask the court to compel logs and data from an entity (in this case, the FCC, to then identify the defendant.