Longtime Facebook executive Andrew Bosworth said in a blunt internal post that the company’s advertising tools were crucial to the election of Donald Trump in 2016 and may help him win again but that executives must resist the temptation to make policy changes that would alter the course of legitimate political debate.

The post, which appeared on the company’s internal systems last week and surfaced in news reports Tuesday, reflected the combination of anguish, defensiveness and brash self-confidence that many of the company’s employees have more privately expressed in the difficult aftermath of Trump’s unexpected victory.

Bosworth’s post also shed light on the thinking within the company’s highest levels as it heads into a new election year amid controversies over its reluctance to police lies by politicians or limit their ability to narrowly target small groups of voters. Critics have said that addressing both issues is key to helping stanch the flood of disinformation on the platform.

“So was Facebook responsible for Donald Trump getting elected? I think the answer is yes, but not for the reasons anyone thinks,” wrote Bosworth, the company’s vice president for augmented and virtual reality and long considered close to chief executive Mark Zuckerberg.

Bosworth dismissed the idea that Russian efforts to manipulate U.S. voters over Facebook, a subject of extensive government investigation and journalistic scrutiny, were crucial to Trump’s victory. Bosworth, who shared his post publicly after the New York Times published it, also played down the importance of the use of Facebook data by the political consultancy Cambridge Analytica, which worked for the Trump campaign and boasted of its ability to target ads using psychological profiles of voters derived from their social media posts.

Rather, said Bosworth, who ran advertising at Facebook for several years, President Trump “got elected because he ran the single best digital ad campaign I’ve ever seen from any advertiser. Period.”

Bosworth, a self-proclaimed liberal who donated heavily to 2016 Democratic Party nominee Hillary Clinton, particularly praised Trump’s leading digital-advertising adviser in 2016, Brad Parscale, who is now managing Trump’s reelection campaign. Parscale has publicly cited Facebook’s ability to reach small numbers of voters with targeted messages, using tens of thousands of versions of ads per day to maximize the campaign’s effectiveness, as essential to Trump’s victory.

“Parscale and Trump just did unbelievable work,” Bosworth wrote in his post. “They weren’t running misinformation or hoaxes. They weren’t microtargeting or saying different things to different people. They just used the tools we had to show the right creative to each person. The use of custom audiences, video, ecommerce, and fresh creative remains the high water mark of digital ad campaigns in my opinion.”

That comment and some others puzzled some who read the post. The term “microtargeting” is often understood to include the company’s powerful Custom Audiences tool, which Trump used and allows advertisers to identify targets by a wide range of factors — location, age, income, interests, education or even visits to a certain website or Facebook page.

Bosworth’s post generated significant commentary and debate in the comments section below it and on Twitter. Facebook employees also had more private conversations in which they questioned some of his assertions.

Sriram Krishnan, a former Facebook executive who worked on some of the Facebook ad platforms in question before leaving the company in 2016, wrote on Twitter that Bosworth’s post showed off the good aspects of Facebook’s company culture and its “ability to be self-critical and introspective and debate things internally.”

Krishnan concurred with the memo’s claim that Cambridge Analytica did not benefit Trump, calling the unauthorized use of data “a total non-event for the 2016 election.” However, in his Twitter posts, Krishnan also noted that Bosworth identified a common reaction inside tech companies, where media criticisms are rejected “because of one incorrect detail” while ignoring the broader point.

Alex Stamos, Facebook’s former chief security officer, also weighed in on Twitter. Bosworth’s analysis of Facebook’s role in the 2016 election was correct, Stamos wrote, adding: “Where I disagree with Boz is that I think limits on targeting for political and issue ads are neutral and fair in the long-run and conducive to healthier democracy. Same with a tightly drawn standard on false claims about opponents. Neither are an attack on Trump.”

Bosworth’s post is reflective in sections. He urges the company to not overreact to criticism from the news media — even when employees think all or part of news reports are wrong. And he cites American moral philosopher John Rawls, who died in 2002, who proposed a form of moral decision-making called “the veil of ignorance,” in which people are supposed to propose structures for a society without supposedly knowing factors including their own race, income, education level or gender.

Citing J.R.R.'s Tolkien “Lord of the Rings” epic, Bosworth also expressed serious concern about the possible corrupting influence of Facebook’s power, comparing it to the ring carried by the hobbit Frodo Baggins.

Bosworth says the current election season carries a similar moral risk, with regard to how Facebook sets advertising policies that could affect Trump and other politicians, who have vociferously opposed possible new restrictions.

“That brings me to the present moment, where we have maintained the same ad policies,” Boswell wrote. “It occurs to me that it very well may lead to the same result. As a committed liberal I find myself desperately wanting to pull any lever at my disposal to avoid the same result. So what stays my hand?”

“I find myself thinking of the Lord of the Rings at this moment. Specifically when Frodo offers the ring to Galadrial and she imagines using the power righteously, at first, but knows it will eventually corrupt her. As tempting as it is to use the tools available to us to change the outcome, I am confident we must never do that or we will become that which we fear.”

One Facebook employee, speaking on the condition of anonymity, said in an interview that debate inside Facebook was limited to reasonable changes. “We could pull a lever, as in disallow political ads, disallow certain kinds of targeting, enforce stricter standards on racism in ads,” the employee said. “No one at any point has ever suggested we deliberately scuttle Trump’s campaign. That’s pretty inconceivable.”