One of the mysteries of the English language finally explained.
A person who traditionally votes for the Democrats, but who as an admirer of Reagan or his policies may be (or has been) influenced to vote for the Republicans (now historical). Hence in later use: a conservative Democrat.
1970s; earliest use found in The Lincoln Star. From the name of Ronald Reagan + democrat.
Reagan Democrat/ˌreɪɡ(ə)n ˈdɛməkrat/
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