How do you confirm the election results itself though, when the election purveyors can't be trusted? Statistical polling has been a third-party check on elections for a century.
To answer your question, you volunteer locally so that you're involved in the process, or you encourage somebody that you trust to do so, or somebody they trust, etc... You validate it by doing it validly.
Also, yes, we can and should be volunteering locally. AND ALSO we can have independent statistical review.