In response to the calls of his country and his clients, A.B. Culvahouse often appears in the wrong place at exactly the right time.

Culvahouse, 70, crafted a career spanning more than 40 years in Washington, D.C., as an East Tennessee emigrant dedicated to public service who rose to lead one of  thecountry’s top law firms. His work has revolved around presidents in peril, from Watergate to Iran-Contra, and his business card is within reach whenever Republicans need to vet candidates for the nation’s highest offices.