Debbie Wasserman Schultz, chairperson of the Democratic National Committee, has been dropped as a speaker at this week's convention after leaked emails suggested the panel showed bias against Bernie Sanders in the party primaries, CNN said on Sunday.
Meanwhile, Sanders said that Schultz should resign, saying a new leader is needed to focus the DNC on defeating Donald Trump, attracting young voters and improving the economy.
The DNC will convene for three days on Monday in Philadelphia and is widely expected to endorse Hillary Clinton's presumed candidacy for U.S. president in the November elections, after her triumph over Sanders.
CNN quoted an unidentified Democrat as saying that Wasserman Schultz "will not have a major speaking role," at the meeting, and calling it a decision intended "to keep the peace."
Wasserman Schultz will likely wrap the opening gavel but then bow out without speaking after the information revealed by some of 20,000 emails leaked by Wikileaks since Friday.
"She's been quarantined," a top Democrat is quoted to have said.
Emails from January 2015 through May 2016 leaked from seven DNC officials, Wikileaks says, feature Democratic staffers seeking ways to undercut Sanders' candidacy, CNN and other media reported.
One email features DNC staffers appearing to ponder ways to undercut Sanders, who had late in the primary endorsed Wasserman Schultz's primary opponent in her Florida congressional race.
In another, on May 5, a DNC employee asked colleagues to "get someone to ask about his belief" in God, without mentioning Sanders by name, and suggested it could make a difference in Kentucky and West Virginia.
"This could make several points difference with my peeps. My Southern Baptist peeps would draw a big difference between a Jew and an atheist," DNC chief financial officer Brad Marshall wrote.
Another email seems to show the DNC seeking to reference Bernie Sanders' Jewish faith to weaken him in the eyes of Southern voters.
Marshall did not respond to a request by CNN for comment.
Baltimore mayor and DNC Secretary Stephanie Rawlings-Blake denied that Clinton's camp was treated more favorably by the committee, CNN said.
"My expectation is beyond your opinion about a candidate, that you act evenly. All of the officers took a pledge of neutrality and I honored that, and I take that very seriously," Rawlings-Blake told CNN's Poppy Harlow.
She added, "I know that the chair will hold those employees accountable if they're found to have acted outside of that neutrality and even-handedness."
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