In a letter to Twitter CEO Jack Dorsey dated Tuesday, Harris pointed to six tweets Trump has sent since last Friday that Harris says violated Twitter's rules.
Harris said that Trump has used his account to "target, harass, and attempt to out the whistleblower" whose allegations about Trump's call with the leader of Ukraine prompted Democrats to launch an impeachment inquiry.
"President Trump also published the following tweet suggesting that violence could be incited should Congress issue formal articles of impeachment against him," she wrote, highlighting a tweet Trump sent on Sunday that read: "....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." The tweet was a selective quote of a supporter on Fox News.
Harris also pointed to tweets Trump sent that said Rep. Adam Schiff should be "questions at the highest level for Fraud & Treason."
"These are blatant threats," Harris wrote to Dorsey, "We need a civil society, not a civil war."
Harris pointed to how Twitter previously banned high-profile users from its platform, like the conspiracy theorist Alex Jones.
"No user, regardless of their job, wealth, or stature should be exempt from abiding by Twitter's user agreement, not even the President of the United States," she wrote.
A Twitter spokesperson confirmed to CNN on Wednesday that company received the letter and intends to respond.
Twitter announced in June that some tweets from world leaders that break its rules would not be removed from the platform if the company decided they were in the "public interest." Twitter said it would instead put a disclaimer on the tweets explaining that although they broke the company's rules they would not be removed.
Twitter has not labeled any of Trump's tweets in this way.
When Trump used racist language to attack four progressive Democratic congresswomen in July, a Twitter spokesperson told CNN the tweets did not break the company's rules.