MEXICO CITY—Mexican authorities scrambled over the weekend to locate Diego Fernández de Cevallos, a former presidential candidate and wealthy lawyer whose disappearance is the most high profile apparent kidnapping since President Felipe Calderón began his war on drugs in 2006.

Mr. Fernández, who ran for president with the National Action Party, or PAN, in 1994, disappeared Friday night in the central state of Querétaro, officials from the attorney general's office said.

His...