Every time I look for information on this, I don’t find any satisfactory answers. They all tend to be speculative with no specific mention of cause
This question has been answered before by u/Samuel_Gompers and u/trilldax. Please see [this] (https://www.reddit.com/r/AskHistorians/comments/yczua/can_someone_address_a_brief_history_of_democrats/), [this] (https://www.reddit.com/r/AskHistorians/comments/t5y3m/it_seems_that_during_the_civil_war_and/), and [this] (https://www.reddit.com/r/AskHistorians/comments/12vvo4/how_and_when_did_the_republican_party_transition/) link.