C. MICHAEL ARMSTRONG

A former CEO and chairman of AT&T from 1997 until he resigned in 2002. He led AT&T to acquire two of the largest cable television companies in 1998 but had to break up the new company in 2001 in the wake of the dot-com bust. Armstrong was also a former Citigroup board member from 1989 to 2010. He was criticized for his role in Citigroup's financial struggles during the 2007 financial crisis.

Born in Detroit in 1938, Armstrong is also a member of the Council on Foreign Relations. Prior to joining AT&T, he held high-level positions at IBM, where he worked for 31 years, and at Hughes Electronics, where he helped launch DirecTV.