Stung by obscene and pointed criticism, Representative Devin Nunes, a Republican from California, said he was suing Twitter and three users for defamation, claiming the users smeared him and the platform allowed it to happen because of a political agenda.

The complaint, which Fox News reported was filed in Virginia on Monday, seeks $250 million in damages. In making his case, Mr. Nunes, a loyal ally of President Trump and the former chairman of the House Intelligence Committee, repeated several common Republican complaints that Twitter has repeatedly denied: that it censors Republicans, “shadow bans” their accounts and actively helps their opponents.

Though absorbing criticism comes with the territory for politicians, the complaint described the objectionable tweets from the three users as something “that no human being should ever have to bear and suffer in their whole life.”

To make his case, he cited a wide variety of tweets that included accusations of criminal misconduct, crude jokes at his expense and relatively banal criticism. The complaint says the tweets “falsely stated” that Mr. Nunes had brought “shame” to his family and that he was voted “Most Likely to Commit Treason” in high school, and that one of them included a cartoon image of a sexual act with Mr. Trump and President Vladimir V. Putin of Russia. The complaint lists dozens of other tweets he found insulting.

Mr. Nunes singled out Liz Mair, a Republican strategist who said on Twitter that she would not comment on the lawsuit, and two parody accounts: @DevinNunesMom, which was suspended last year, and @DevinCow, which is still active. The complaint says that Ms. Mair coordinated with the anonymous accounts on “a vicious defamation campaign” but did not offer evidence she was behind them or communicated with them, except for one tweet encouraging people to follow @DevinCow.

Experts generally say the law protects large internet platforms like Twitter, Facebook and YouTube from liability based on what their users publish. Section 230 of the Communications Decency Act says they should not “be treated as the publisher or speaker” of the content — allowing the platforms to exist without having to preapprove every post for potential legal issues.

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