Yet the manufactured outrage produced by this anti-Muslim cabal turned what was supposed to be Twitter’s venue for social discourse into a one-way digital highway of harassment and hate.

Key themes included Muslims as subhumans or “Trojan horses” seeking to impose Shariah law on America. Ms. Omar’s hijab was a lightning rod; so was Ms. Tlaib’s Palestinian heritage. Forty percent of those attacking Ms. Omar for her comments on Israel also used overtly Islamophobic or xenophobic language, like “@IlhanMN I stand with Israel and denounce Mohammad as a false prophet and Islam the work of Satan.”

“Terrorist” and “jihadi” were among the most frequently occurring words in tweets tagging Ms. Tlaib. Disinformation and unproven allegations originating on obscure blogs, including stories that Ms. Omar supported female genital mutilation and had married her brother, were widely retweeted and picked up by an array of right-wing sites such as PJ Media.

We found something else that was striking. America’s anti-Muslim narrative has long been shaped by an Islamophobic lobby that the Center for American Progress has called “Fear Inc.” Most of those “old school” figures were absent from the hate-filled narrative around Ms. Omar and Ms. Tlaib, eclipsed by a new cadre of internet-savvy actors that have seized control of the anti-Muslim narrative, including the provocateur Laura Loomer, who has been banned from most social media platforms; Alphanews.com, a crowdsourced Minnesota aggregator; and an array of bots that mask the real faces behind them.

Jack Dorsey, the chief executive of Twitter, recently announced that the platform would refuse to accept most political advertising, because it “brings significant risks to politics, where it can be used to influence votes to affect the lives of millions.”

But paid advertising is just part of the problem. The online cacophony of hate Ms. Omar and Ms. Tlaib encountered had nothing to do with political ads. The extent to which trolls co ntrolled th e narrative on Twitter, at no cost, raises questions about the nature of public discourse in the age of social media and the challenges for Muslims and candidates from other minority groups seeking a voice in the political process in the 2020 election cycle.

There was no magic to what we did. If we can find the trolls, so can Twitter. If we can single out those using hate speech, so can Twitter. If we can map the bot networks, so can Twitter. This is about the platform taking responsibility and systematically enforcing its own standards, not passing the buck and blaming advertising while ignoring the fact that it is the true currency of Twitter — the tweets themselves — that bring “significant risks to politics” and “the lives of millions.”

Lawrence Pintak (@lpintak) is a professor at the Edward R. Murrow College of Communication at Washington State University and author of “America and Islam: Soundbites, Suicide Bombs and the Road to Donald Trump.” Jonathan Albright (@d1gi) is the director of digital forensics at Columbia University’s Tow Center for Digital Journalism. Brian J. Bowe (@brianjbowe) is an associate professor at Western Washington University.

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