The cellphone video shot in the dark by a woman in a parked car appeared to show something ominous: a man closing the doors of a white van and then rolling a wagon with a large box into a Detroit election center.
Within hours, the 90-second clip was being shared on news sites and conservative YouTube accounts, offered as apparent proof that illegal votes were being smuggled in after polls closed. Prominent Republicans, including Eric Trump, one of the president’s sons, amplified the falsehoods on social media. Within a day, views of the video shot up past a million.