As an election officer in Virginia, I can tell you that such observers would be violating the law in this state. State law provides for one authorized representative from each party to sit behind each election officer that has a copy of the poll book. That is part of each party's "get out the vote" efforts. Anyone else who hangs around inside the polling place will be asked politely to leave. Non-compliance is a Class I misdemeanor. If anyone else wants to, they can be present when that precinct confirms the vote count - but (1) the person has to be there before the polling place closes and must sign in as being there for that purpose, (2) no cell phones during the count (to prevent reporting of partial totals), and (3) the person cannot leave until all of the counting is complete (security). A person may take a cell phone photo of the final count at the precinct.
Anyone with more detailed questions can PM me.