What were the main driving factors of the reversal of policies in the Democrat and Republican parties in the US?

by Reustag

Out of just general curiosity, I want to know why such a switch happened, when it at first glance makes more sense for them to have the same general stances as way in the past. Are there any specific events/laws/acts that stand out in nudging it along?

histprofdave

There are a few posts in the FAQ, and I also added some additional detail in this thread.