True but this happens already, so each of the candidate's election teams or people on the ground in that area are already getting a rough of estimate of how many votes their candidate is getting and if they have resources they can bring in more people to vote for their candidate, this is especially true for poorer countries where people sell their votes for money. Also do you think this is a big enough problem that someone is changing who to vote for at the end if they are only being influenced by their own mind and not external factors? After all it is their right who to vote for.