What Did The Emperor Know And When Did He Know It?

It appears that the destruction of the Death Star was an inside job.  The logic is so obvious, yet how did I miss it all of these years?  Though without Jar-Jar Binks (the galactic equivalent of Cynthia McKinney, though probably slightly less hated and a good bit more intelligent), who was there to ask all of the tough questions?  Needless to say, I will not be voting for Emperor Palpetine in the upcoming elections; this has badly shaken my faith in the galactic empire.