peed in the punchbowl
Slang phrase meaning figuratively to spoil a good thing or favorable situation by some erring, usually small, behavior.
Michael Dukakis seemed like a good presidential candidate; but he peed in the punchbowl by revealing he had been treated for depression.
Oprah Winfrey's TV network was going well until her CEO peed in the punchbowl with her incompetence and was fired.
Oprah Winfrey's TV network was going well until her CEO peed in the punchbowl with her incompetence and was fired.