PHILADELPHIA—The chairwoman of the Democratic National Committee resigned Sunday after a trove of emails were disclosed showing DNC officials had worked to undermine the underdog presidential campaign of Vermont Sen. Bernie Sanders.

Debbie Wasserman Schultz, a Florida congresswoman, said in a statement that she would leave her post at the DNC at the end of this week’s convention. She said she would still open and close the gathering and would address the delegates.

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