Poll watchers – observers who can report voting problems to local officials – operate under strict rules. But President Trump’s call for his supporters to guard polling places during this election has raised concerns about the potential for voter intimidation.

Retro Report is a nonprofit news organization exploring the history and context behind today’s headlines. It has produced more than 200 short documentaries and video series and partnered with The New York Times, The New Yorker, PBS, NBC, Politico, The Guardian, Univision, Quartz and others.

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