I keep hearing this - you're going to have to substantiate it. I remember nothing of the kind happening to Reagan's base - hell, he left office with a 60% approval rating.
Perhaps there were some dissaffected libertarians or reagan democrats, but whats happening to Bush today is in NO WAY similar to Reagans last term.
I don't remember it either, but I do seem to recall some intramural squabbles for power during the late Reagan era. Hardly a matter of any consequence to the base though.