Before the horrendous assassination attempt on Arizona Congresswoman Gabrielle Giffords and the shooting of 20 people, leaving six of them dead, Giffords knew that she had been specially marked by by her opponents. Tea Party conservatives wanted her out of office, even though she is a conservative Democrat, and weren't afraid to use thinly-veiled calls for violence against her to achieve their goal.
Her opponent in her 2010 Congressional race staged an event to "target" her by offering voters a chance to shoot an M16. Her Tucson office had been vandalized after her vote on the health care bill in March of last year, as had other Congressional offices. And Sarah Palin advocated for getting her out of office -- her PAC site posting a map of the country with a graphic of the cross-hairs of a gun-sight on each of the offices she wanted her chosen candidates to win, one of those being Giffords'. The Sarah Palin PAC site has taken down the map, but you can see it at her Facebook Fan Page. Spokespeople for Palin now are claiming that the marks on the map were not intended to be cross-hairs -- you be the judge. It would certainly be consistent with her continuing theme of calling on conservatives to "reload."
Palin certainly isn't the only extreme conservative who's felt that it's appropriate political gamesmanship to use slightly veiled language of violence to promote political agendas.