Mark Twain's Quote on Politicians

I really don't know the context behind what Mark Twain was quoted as saying that "politicians and diapers must be changed often, and for the same reason."  Did he have a terrible time dealing with politicians?  I've been trying to do a bit of research about this but I just couldn't find any affirmation on this quote.  It is a great quote for people aspiring for public office, and a cheeky way to get the attention of voters.

It is a great quote though, that speaks volumes!  I've seen on the web certain personalities and politicians using this quote in their speeches.  It does make for a good conversation piece and with the media landscape nowadays, media handlers for politicians can use this to make for a good sound bite.