JFK - his death enabled a vast expansion of the Vietnam War, while ending his initiatives for world peace
MLK, Jr. - his death doomed to failure the Poor People's Campaign and his struggle for social justice in the US
RFK - his death enabled Nixon's agenda, while ending any chance to discover who really killed JFK
Senator Paul Wellstone - his death facilitated the War on Terror, while ending all official efforts to discover what really happened on 9/11
Justice Antonin Scalia - the impact of his death is yet to be determined, but it could be profound (see http://www.americanthinker.com/blog/2016/02/the_impact_of_scalias_death_on_the_major_court_cases_to_be_decided_this_term.html)
Perhaps none of these deaths occurred from anything other than what the official stories would have us believe.
But don't ever think there are no political assassinations in the US. That's a far less likely possibility than anything suggested by us "conspiracy theorists".