Had Jesse Jackson won the presidency in 1988, who would have been a Reagan '80/'84 voter who then voted for Jesse Jackson for president, other than a African American or Latino/Asian voter?
A suburban white female voter?
It's not exactly what you called for, but it's pretty close.
Muhammad Ali voted for Jesse Jackson in the 1984 primary, and then Reagan in the General election.
nytimes.com/1984/10/03/us/campaign-notes-muhammad-ali-switches-his-support-to-reagan.html?n=Top%2FReference%2FTimes+Topics%2FPeople%2FA%2FAli%2C+Muhammad
