As long as THEY let people vote as they did THEY commited a felony, if any.
This article is ridiculous. No prosecutor in their right mind would take on such a case.
You're right. Every poll worker is required to attend a 2-3 hour training session before each election, regardless of how many times they have worked the polls. Handling cross-over votes is a part of every training for primary elections. If a person wants to cross over, there is nothing that keeps him from doing so.