Mark Zuckerberg this week doubled down on his decision to allow unchecked political advertising on Facebook, even though pressure intensified for him to ban it following Twitter's decision to do so.
Some say that by allowing even political adverts which contain falsehoods, the Facebook chief executive is putting profits ahead of protecting US democracy. Elizabeth Warren, one of the Democratic frontrunners for next year's presidential elections, has called Facebook a "disinformation-for-profit machine".
• Twitter to ban all political ads worldwide amid 2020 election uproar
• Five takeaways from Zuckerberg's Libra testimony
• Fact-checking Facebook's fantasies
• Facebook is the world's most powerful adolescent
But analysts say that with political advertising proving a relatively minor role in Facebook's revenues, a more relevant consideration is the possible reaction of Republicans, who used Zuckerberg's platform to such effect at the previous election.
Youssef Squali, an analyst at SunTrust Robinson Humphrey, said: "In a way it would be easier for Zuckerberg to step away from political advertising, given it contributes so little to the company's sales.
"But if he does so, Republicans are going to jump on him and accuse him of suppressing free speech. So he has decided to fight for it on moral grounds."
The Facebook chief executive predicts that his company will get just 0.5 per cent of its sales next year from political advertisements. Based on analyst estimates, that would equal about US$400 million ($622.2m).
The reach it buys for political campaigns, however, is invaluable, say experts, especially for fundraising leads.
"If you really want to persuade someone, you need video, which is why television works best for that," said Travis Ridout, professor at the Wesleyan Media Project, which tracks political advertising.
"But if you want email addresses so that you can bombard people with marketing material and requests to donate, that's where you need social media."
Brad Parscale, the campaign manager for Trump 2020, told The Washington Post last year that the campaign would rely less on social media than it did last time, not least because it already has so many voters' email addresses and telephone numbers.
Parscale's reaction this week to Twitter's political advertising ban told a different story.
"This is yet another attempt to silence Conservatives, since Twitter knows President Trump has the most sophisticated online programme ever known," Parscale said.
Tim Lim, a former Democratic digital adviser, said: "Twitter shutting down political advertising is probably better for the Democrats than the Republicans. Because the president spends so much time on there, it has become a place for conservatives to organise."
The spending figures also show how much Trump is relying on social media to be able to reach the kind of disaffected voters he counted on so successfully three years ago.
But they also show that Facebook, rather than Twitter, is the real prize.
Since the beginning of the year, the president's campaign has spent US$15.7m advertising on Facebook, and a further US$9.4m on Google, according to data compiled by Bully Pulpit Interactive, a communications agency. That far outstrips any of his Democratic challengers.
The agency does not gather data on Twitter advertisements but, for comparison, campaigns spent less than US$3m on the platform in the run-up to the 2018 midterm elections, according to Ned Segal, Twitter's chief financial officer.
Zac Petkanas, a Democratic party strategist, said: "You use Twitter to reach the chattering classes and help shape news coverage. But it is Facebook which gives you significant reach into important voting blocs."
Zuckerberg spent the week defending his position, issuing some uncharacteristically robust arguments against his detractors. After being criticised by the screenwriter Aaron Sorkin for promoting misinformation, Zuckerberg fired back in a Facebook post.
Quoting Sorkin's own words from his film The American President, Zuckerberg posted: "You want free speech? Let's see you acknowledge a man whose words make your blood boil, who's standing centre stage and advocating at the top of his lungs that which you would spend a lifetime opposing at the top of yours."
Some predict that as the criticism of his company mounts, Zuckerberg might yet change course.
"There is so much pushback, even from average Facebook users, that I wonder if ultimately he will decide to go the same way as Twitter," Squali said.
If that happens, it is likely to cheer candidates like Warren, and anger the leaders of Trump's campaign.
But some worry that it could also prove harmful for US democracy in the long term.
"At least some portion of the money is going to get shifted to much less transparent organisations that are much harder to regulate, and that is a pretty scary place to be," said Jessica Alter, co-founder of Tech for Campaigns, which partners tech workers with political campaigns.
"The Twitter is ban is mostly inconsequential," she added. "But a broad ban would be terrible."
Written by: Kiran Stacey and Hannah Murphy
© Financial Times