California senator and 2020 presidential candidate Kamala Harris has formally asked Twitter to suspend President Donald Trump’s account, following Trump’s attacks on a whistleblower and his claim that impeachment would start a civil war. In an open letter to Twitter CEO Jack Dorsey, Harris says that Trump has used Twitter to “target, harass, and attempt to out” the person who filed an explosive complaint about Trump pressuring Ukraine to dig up dirt on rival candidate Joe Biden.

Trump has been tweeting angrily about the complaint for several days now. Harris cites multiple messages where he calls the whistleblower “a spy” as well as a tweet where he called to arrest Rep. Adam Schiff (D-CA), who has helped lead the investigation into Trump’s actions, for “fraud and treason.” Offline, Trump has arguably insinuated that the whistleblower should be executed for spying — something Harris says makes his tweets more threatening. “These tweets should be placed in the proper context,” she writes.

Around the same time, Trump quoted a Fox News claim that “if the Democrats are successful in removing the president from office (which they will never be), it will cause a civil war-like fracture in this nation from which our country will never heal,” which Harris also notes. “These tweets represent a clear intent to baselessly discredit the whistleblower and officials in our government who are following the proper channels to report allegations of presidential impropriety, all while making blatant threats that put people at risk and our democracy in danger,” she writes.

INBOX: Kamala Harris pens formal letter to Jack Dorsey asking him to kick Trump off Twitter, writing "these are blatant threats. We need a civil society, not a civil war. pic.twitter.com/zbC4dKUyEu — Alex Thomas (@AlexThomasDC) October 2, 2019

Harris also publicly highlighted another Trump tweet calling impeachment a “coup” and discussed banning Trump from Twitter in a CNN interview.

Twitter told The Verge that it has received the letter and plans to respond to Harris’s concerns. However, it almost certainly won’t suspend Trump’s account. The platform allows politicians with a sufficient number of followers to break its rules, asserting that it’s “in the public interest” for users to see the tweets. It reserves the right to flag particularly bad tweets, but it’s never even reached that point with Trump, despite previous controversies. In 2017, it cited “public interest” to justify letting Trump threaten war against North Korea in a tweet, although it did later delete a Trump video that included copyrighted music from a Batman film.

It’s unclear how Twitter is generally policing veiled threats of civil war. The company told BuzzFeed that it wouldn’t remove a tweet from a prominent militia group claiming that the idea of a “full-blown ‘hot’ civil war” was “increasingly on people’s tongue.” Like its competitor Facebook, the social network is struggling to moderate threatening political language on its platform without being seen as taking an ideological stance — something Harris is attempting to highlight, if not necessarily change, with her letter.

Update 9:25AM ET: Added statement from Twitter.