Dozens of other journalists disagreed with that view, offering public support. The Washington Post’s media columnist Margaret Sullivan, for one, advised CNN to sue the White House on First Amendment grounds.
The move against Mr. Acosta also came shortly after a pipe bomb turned up at CNN’s New York headquarters. The suspect arrested in the case, Cesar Sayoc Jr., had been photographed at a Trump rally holding an anti-CNN sign, and the authorities found a “CNN Sucks” sticker on his van.
At Infowars, the imprimatur of the White House was a welcome development.
The site has lost a chunk of its audience since being banned by several major online platforms this summer, including Facebook, YouTube, Twitter and Apple’s App Store. Mr. Watson, who rose to prominence on the site, has kept his social media and YouTube accounts, providing one of the few remaining means for Mr. Jones to reach a mainstream audience.
The video tweeted by Ms. Sanders makes it appear that Mr. Acosta is making forceful, sustained contact with the intern’s arm. The Infowars video also has no sound, so that Mr. Acosta’s “pardon me” is not heard.
“If you look at original, higher-quality videos from other vantage points, you can more clearly see that while there was some contact between the reporter and intern, he did not strike her as his hand comes down,” said Hany Farid, a digital forensics expert at Dartmouth College who analyzed the clip for The Times.
The news conference was broadcast on major cable outlets, including the public affairs network C-SPAN, meaning that she had other options than to use a clip put together by a contributor to a notorious site.
Infowars seized on the publicity that went with Ms. Sanders’s use of the clip, posting incendiary items under headlines like “Did Jim Acosta Assault a Woman?” Mr. Jones did not respond to a message left on his cellphone. Mr. Watson, who is based in Britain, did not respond to requests for comment.