.... is a lot less than is widely thought.
After the Tucson massacre there was a concerted campaign by the media, led by the New York Times and the local sheriff, to smear their political opponents by linking the killer to "polarising rhetoric", which was naturally only found on the right not the left.
So you'd think with such a concerted campaign of vilification would have results. Actually no, according to a Pew Survey, the proportion of the US population who believe that the shooting was linked to political rhetoric is.... 0.6%.
There are probably more people who claim to have been abducted by aliens.