No, but there has been an insidious conspiracy by sleaze-merchants like Jim Garrison, Mark Lane, Oliver Stone, L. Fletcher Prouty, Jesse Ventura, Jack Martin, Jim Marrs, etc to convince people that there was a conspiracy in order to make a buck off of the assassination of President Kennedy.
I'd highly recommend this website for anyone who thinks there was a conspiracy, as well as
Reclaiming History by Vincent Bugliosi (the latter of which I have read cover-to-cover and don't think any rational human being could read and then honestly believe there was a conspiracy):
http://mcadams.posc.mu.edu/home.htmI'd especially recommend this for folks who think Kennedy was trying to get out of Vietnam when he was killed or even that he was any sort of beacon of liberalism.
http://mcadams.posc.mu.edu/stjohn.htm