Ronald Reagan was often referred to as the "Teflon President,"  because despite the indictment, conviction, or investigation of 138 administration officials during his two administrations, nothing ever stuck to him.  Except this incident, the biggest presidential scandal since Watergate.

Suggested reading if you want to learn more:
Kornbluh, Peter; Byrne, Malcolm (1993). The Iran–Contra Scandal: The Declassified History. New York: New Press.

Walsh, Lawrence E. (1997). Firewall: The Iran–Contra Conspiracy and Cover-up. New York: Norton & Company.