Are we talking about real, actual, measurable, and provable voter fraud or "my candidate lost so there had to be voter fraud" voter fraud?
“real, actual, measurable, and provable voter fraud”
You see, it depends who gets to investigate it.
I know an old attorney who used to explain what he wanted to see when it came to assigning attorneys to projects.
He said they had to be capable, highly motivated, and honorable.
If the investigators are incompetent, corrupt or just “mailing it in” you will never “prove” substantial voter fraud.