Legitimately registered voters are allowed to show up, vote, and then leave in an orderly manner. They are not allowed to loiter around the polls all day trying to influence the outcome of the election. And "observers" who aren't even legally registered to vote sure as hell shouldn't be doing that either.
Why are so many people getting uber-defensive about foreigners influencing the election? Dude, they are only here to OBSERVE. They are an impartial 3rd party just as officials in a football game are. They are the only impartial observers you're going to get. Having locals view the polls is like having the umpire of a baseball game be a member of the home team; he would have a vested interest in turning a blind eye to malfeasance.
Getting your hackles up about foreign observers is a sure sign that you're jingoistic and think the USA can do no wrong. And, my, how wrong such thinking is.