Really the only prominent Republican of the last century who I can imagine as a Liberal would be Eisenhower
Does Lincoln Chafee count? How about Gerald Ford? Or Rockefeller?
Definitely all PC before 1993. After 1993, defect to the Liberals at some point (like Garth Turner or Scott Brison). Only Jim Jeffords can I imagine starting out as a Liberal, and others in that mold like John Anderson.
(This is a little bit altered by the fact that the Republicans were traditionally dominant in the Northeastern US, while the Liberals were dominant in the historically similar Maritimes. Chafee might have begun as a Liberal--but only if his father had also been a Liberal.)
