What is an exit poll?
how have exit polls influenced the outcome of state and local elections?

This is really late but it is a poll that people take as they are leaving an polling place, asking how they polled.  They have influenced the outcomes of state and local elections because other people see how many votes each person gets and if you have no idea who is running or whatnot and want to vote, you'd vote for the majority one because more people voted for him or her.  They hop on the bandwagon. Hope this helps