The US Democratic Party chair says she will resign as a row over leaked emails threatens efforts for party unity at the presidential nominating convention.
Debbie Wasserman Schultz's move follows a leak of emails appearing to suggest that party insiders tried to thwart the campaign by Hillary Clinton's rival.
Bernie Sanders had pressed for Ms Wasserman Schultz to quit on the eve of the convention.
Mrs Clinton is to be officially nominated at the Philadelphia meeting.
Vermont senator Mr Sanders had said Ms Wasserman Schultz "should not be chair" of the Democratic National Committee.
"And I think these emails reiterate that reason why she should not be chair," he told ABC's This Week programme.
More than 19,000 internal DNC emails were published by the WikiLeaks website on 22 July, from the accounts of seven leading figures.
Some revealed officials looking at ways to undermine Mr Sanders' campaign, including using his faith.
Is it enough? By BBC North America reporter Anthony Zurcher
Democratic National Committee head Debbie Wasserman Schultz had become the face of the obstinate party hierarchy for progressive Bernie Sanders supporters. Now they have claimed her (political) head.
She probably would have survived the tendentious 2016 Democratic primary campaign were it not for the DNC email hacks, which showed that she helmed an organisation that chafed at the rise of a candidate who didn't even identify as a member of the Democratic Party until recently.
The revelation that those in the heart of the Democratic establishment sought to undermine the anti-establishment Sanders is roughly on a par with police Capt Renault's professed shock that gambling was taking place in the Casablanca club he was raiding, as a waiter hands him his winnings.
Once the email evidence was laid bare, however, Ms Wasserman Schultz's fate was sealed. Hillary Clinton and her campaign are desperate to put a unified face on their party - particularly in order to offer a stark contrast with the Republican discord last week.
If that has to come at the expense of Ms Wasserman Schultz's political future, they probably consider it a small price to pay. There's no guarantee that just one sacrifice will be enough to soothe the Bernie brigades, however.
They have long suspected the Democratic Party was out to get them. Today they have some proof.
Ms Wasserman Schultz said she would "step down as party chair at the end of this convention" but expressed hope that all party supporters would rally behind the event.
"We have planned a great and unified convention this week and I hope and expect that the DNC team that has worked so hard to get us to this point will have the strong support of all Democrats in making sure this is the best convention we have ever had," she said in a statement.
She added that she still plans to carry out her duties to formally open and close the convention, and will also speak at the gathering.
President Barack Obama expressed gratitude for her services to the party in a statement.
Mr Sanders and his supporters have also expressed disappointment at Mrs Clinton's choice of Virginia Senator Tim Kaine as her running mate, preferring someone further to the left.
But Mr Sanders did say: "I have known Tim Kaine for a number of years... Tim is a very, very smart guy. He is a very nice guy."
Mrs Clinton's campaign received a boost on Sunday with the announcement that Michael Bloomberg, who was elected New York mayor as a Republican, will speak to endorse her this week.
The Democrats' four-day convention starts on Monday, with speeches by First Lady Michelle Obama and Mr Sanders.
It comes just after the Republican convention that saw Donald Trump declared the Republican presidential nominee.