The "past exonerative tense" is a witticism coined by William Schneider of the New York Times to describe the rhetorical tactic of speaking in the passive voice in order to distance oneself from blame. The tactic is most famous for being invoked by politicians.

The classic example of this usage was the 1986 utterance of "Clearly, mistakes were made..." by then president Ronald Reagan to describe the actions of officials in his administration during the Iran-contra affair, who sold arms to Iran to fund rebels in Nicaragua.

Other instances can be found in statements by Bill Clinton, Alberto Gonzales, John E. Sununu, and George W. Bush, among others.

References

• Familiar Fallback for Officials: 'Mistakes Were Made' (New York Times article)
• Passively fascinating (The Economist article)