Casey Chin; Getty Images Last week, as thousands of Central American migrants made their way northward through Mexico, walking a treacherous route toward the US border, talk of ” the caravan ,” as it’s become known, took over Twitter. Conservatives, led by President Donald Trump, dominated the conversation, eager to turn the caravan into a voting issue before the midterms. As it turns out, they had some help—from propaganda bots on Twitter. Late last week, about 60 percent of the conversation was driven by likely bots. Over the weekend, even as the conversation about the caravan was overshadowed by […]