Once an anti-Semitic rumor moved from fringe to the mainstream, it took less than two weeks for violence to erupt. The false allegation that liberal philanthropist George Soros was funding or supporting a caravan of Honduran refugees heading to the U.S. spread wildly from a single tweet posted on Oct. 14.
Along with far-right memes, that allegation helped motivate both an alleged mail-bomber and a mass shooter at a Pittsburgh synagogue. The way these messages traveled across the internet in this short time

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