(n.) A scapegoat is an event person or object that is used to lay the blame on for all that goes wrong, regardless of the contributions of others. This will usually carry on until the scapegoat has gone, or has managed to successfully defend itself against the arguements presented to it.
The word comes from Judaism. During mass reconciliation the rabbi would bring a goat to the alter. The sins of the people would be absorbed into the goat, and it would then be killed, its' blood staining the alter until cleansed. This is what Jesus Christ reflected in his crucifixion, being a scapegoat.