Sarah Palin accused critics -- who said she incited the Arizona shootings -- of perpetrating "a blood libel" in a video message hours before President Barack Obama was due to call for unity in mourning for the victims.
In an eight-minute internet video, she said the gunman alone was to blame.
"Acts of monstrous criminality stand on their own. They begin and end with the criminals who commit them," Mrs Palin said. "Journalists and pundits should not manufacture a blood libel that serves only to incite the very hatred and violence they purport to condemn," she continued.
Mr Obama planned to honour the six people who were killed and the 14 wounded when a gunman opened fire on a crowd being greeted by Gabrielle Giffords, a Democratic Congresswoman.
She remained in critical condition in hospital yesterday, with her husband Mark Kelly, an astronaut, at her bedside.
In a speech in Tucson, Mr Obama was expected to focus on a message of healing and to praise bystanders who prevented the gunman from firing more shots.
Jonathan Capehart, a columnist with the 'Washington Post', said: "People will look at this and ask 'did she (Sarah Palin) provide solace or did she only inflame the situation?'"