The 59-year-old lawyer, who endorsed Obama in 2008 and 2012, serves on the board of trustees for the Kennedy Center, co-founded the Edward M. Kennedy Institute for the United States Senate and the advocacy group Common Sense about Kids and Guns.
She has also declined repeated invitations to run for her late husband's Senate seat in Massachusetts.
Members of the USPS Board of Governors are appointed by the president and confirmed by the Senate. The board selects the postmaster general and reviews the policies and spending practices of the postal service, which said Friday that it had wrapped up 2013 with a $354 million loss.
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