Sarah Palin's disturbing decision to place crosshairs on a map of Gabrielle Giffords congressional district may have been the decision that fatally undermined Palin's chances of ever becoming a presidential candidate.

After the shooting, as Giffords new book (co-authored with her husband Mark Kelly) recounts, Palin taped a stung retort calling suggestions she had been rash a "blood libel."

Palin refused to hear any criticism of her decision to target the Arizona congresswoman's district with a crosshairs symbol on her website.

In their new book, quoted on Politico this week, both Giffords and Mark Kelly write that they objected to Palin's imagery, discussing it before the shooting:

"Gabrielle was troubled that her district was one of twenty targeted on Sarah Palin's Facebook page and website," Mark Kelly writes in 'Gabby: A Story of Courage and Hope.'

Kelly writes that his wife had told him that Palin's rhetoric upset her and had no place in political discourse. "It sends the wrong messages," he quotes Giffords as saying. "It's a dangerous thing to do."

Palin has kept a low public profile since she confirmed in October she wouldn't run for president, although she appeared on Fox New last week.

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