Let’s look at the evidence: In 2016, Facebook provided the Trump campaign with embedded staff who helped to optimize its advertising program. (Hillary Clinton’s campaign was also approached, but it declined to embed a Facebook team in her campaign’s operations.) Brad Parscale, the digital director of Mr. Trump’s 2016 campaign and now his campaign manager for 2020, said that Facebook helped Mr. Trump and gave him the edge. This seems to have marked the beginning of a special relationship.

More recently, direct contact between the two men has raised serious questions. Mr. Zuckerberg met with Mr. Trump in the Oval Office on Sept. 19, 2019. We don’t know what was said. But from an interview on the sidelines at the World Economic Forum on Jan. 22, we do know what Mr. Trump said about the meeting: Mr. Zuckerberg “told me that I’m No. 1 in the world in Facebook.” Mr. Trump apparently had no problem with Facebook’s decision not to fact-check political ads. “I’d rather have him just do whatever he is going to do,” Mr. Trump said of Mr. Zuckerberg. “He’s done a hell of a job, when you think of it.”

The president’s 2016 campaign mounted a robust data-centric communications effort and has continued to build on that program over the past few years, using Facebook as a key part of their strategy.

Facebook’s decision not to require fact-checking for political candidates’ advertising in 2020 has flung open the door for false, manipulated, extreme and incendiary statements. Such content is rewarded with prime placement and promotion if it meets Facebook-designed algorithmic standards for popularity and engagement.

What’s more, Facebook’s design tends to obscure the sources of inflammatory and false content, and fails to adequately punish those who spread false information. Nor does the company effectively warn those who are exposed to lies.