If you are too young to remember Ehrlichman or never studied Watergate in depth, he served a couple of roles in the Nixon administration and was convicted of several charges in 1975 related to the cover-up of the Watergate break-in, serving about 18 months in prison.
Trudeau told me something fascinating about Ehrlichman: the guy would write cartoonist asking for originals of strips about him, even excoriations!