There are several famous quotes in this category. The first is attributed to Jose Maria de Eca De Queiroz a 19th century Portuguese writer. See this link
Politicians and diapers should be changed frequently and all for the same reason. (Translated from Portuguese)
Another version is attributed to the U.S. author Mark Twain (Samuel Clemens)
“Politicians are like diapers; they need to be changed often and for the same reason.”
I saw another version when surfing today but there was no source cited.
"" Governments are like diapers.
When they need to be changed,
it’s often for the same reason!""
Commentators on one posting noted that at least diapers are clean when they arrive! None of the websites I searched on this gave the precise source from which the quote was taken.