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Chelsea Clinton interacts with children during a National Day of Service event on the National Mall in Washington D.C. January 19, 2013. REUTERS/Eric Thayer

U.S. Vice President Joe Biden (C) jogs to the stage for remarks after helping assemble care kits for U.S. military service members and veterans at a Unite America in Service event at the National Guard Armory in Washington, January 19, 2013. Biden and his family volunteered for the event during the National Day of Service as part of the 57th Presidential Inauguration. REUTERS/Jonathan Ernst

U.S. Vice President Joe Biden (2nd R) joins volunteers to help assemble care kits for U.S. military service members and veterans at a Unite America in Service event at the National Guard Armory in Washington, January 19, 2013. Biden and his family volunteered for the event during the National Day of Service as part of the 57th Presidential Inauguration. REUTERS/Jonathan Ernst

A volunteer stops to photograph U.S. Vice President Joe Biden as he helps assemble care kits for U.S. military service members and veterans at a Unite America in Service event at the National Guard Armory in Washington, January 19, 2013. Biden and his family volunteered for the event during the National Day of Service as part of the 57th Presidential Inauguration. REUTERS/Jonathan Ernst

Members of the Central Arizona Young Marines attend the National Day of Service event as Washington prepares for President Barack Obama's second inauguration on January 19, 2013 in Washington, DC. The U.S. capital is preparing for the second inauguration of U.S. President Barack Obama, which will take place on January 21. (Photo by Mario Tama/Getty Images)

A woman writes a note to soldiers as part of a National Day of Service event on the National Mall in Washington D.C. January 19, 2013. REUTERS/Eric Thayer

Chelsea Clinton speaks with people at a service summit on the National Mall January 19, 2013 in Washington, DC. Events around the Inauguration started with a national day of service a yearly event where Americans are encouraged to volunteer and contribute to service projects to honor American civil rights leader Martin Luther King. BRENDAN SMIALOWSKI/AFP/Getty Images

Chelsea Clinton speaks at the National Day of Service event as Washington prepares for President Barack Obama's second inauguration on January 19, 2013 in Washington, DC. The U.S. capital is preparing for the second inauguration of U.S. President Barack Obama, which will take place on January 21. (Photo by Mario Tama/Getty Images)

Volunteer Kennedra Tucker poses at the National Day of Service event as Washington prepares for President Barack Obama's second inauguration on January 19, 2013 in Washington, DC. The U.S. capital is preparing for the second inauguration of U.S. President Barack Obama, which will take place on January 21. (Photo by Mario Tama/Getty Images)

President Barack Obama (R) and first lady Michelle Obama speak to volunteers at Burrville Elementary School January 19, 2013 in Washington, DC. The event was part of the National Day of Service, the first official event of the 57th presidential inauguration weekend. (Photo by Martin H. Simon-Pool/Getty Images)

A woman wears a coat with a picture of U.S. Secretary of State Hillary Clinton and the number 2016, a reference to the possibility she might run for president in 2016, as she listens to Vice President Joe Biden speak to volunteers at a Unite America in Service event at the National Guard Armory in Washington, January 19, 2013. Biden and his family volunteered to assemble care kits for U.S. service members and veterans at the event during the National Day of Service as part of the 57th Presidential Inauguration. REUTERS/Jonathan Ernst

Actress Eva Longoria speaks as part of a National Day of Service event on the National Mall in Washington D.C. January 19, 2013. REUTERS/Eric Thayer

Jay Desai, of Washington, front and Ariel Timar, of Cherry Hill, N.J., center, paint a mural as they participate in the National Day of Service on the Mall as part of the 57th Presidential Inaugural festivities, Saturday, Jan. 19, 2013, in Washington, . The two were working on the Greater DC care project that will place the murals in schools and fire stations to help promote volunteerism. (AP Photo/Steve Helber)

People learn CPR as part of a National Day of Service event on the National Mall in Washington D.C. January 19, 2013. REUTERS/Eric Thayer

U.S. Vice President Joseph Biden (2nd L) chats with volunteers as he participates during a Unite America in Service event on the National Day of Service as part of the 57th Presidential Inauguration January 19, 2013 at the DC Armory in Washington, DC. Vice President Biden and his family joined volunteers to pack care kits filled with necessities for deployed U.S. Service Members, Wounded Warriors, Veterans and First Responders. (Photo by Alex Wong/Getty Images)

People use computers during a service summit on the National Mall January 19, 2013 in Washington, DC. Events around the Inauguration started with a national day of service a yearly event where Americans are encouraged to volunteer and contribute to service projects to honor American civil rights leader Martin Luther King. BRENDAN SMIALOWSKI/AFP/Getty Images

First lady Michelle Obama, accompanied by Jeff Franco, executive director of City Year, stains a bookshelf at Burrville Elementary School in Washington, Saturday, Jan. 19, 2013, as the first family participated in a community service project for the National Day of Service, part of the 57th Presidential Inauguration. (AP Photo/Susan Walsh)

US President Barack Obama paints a bookshelf at Burrville Elementary School during Day of Service on January 19, 2013 in Washington DC, as part of the 57th Presidential Inauguration. Americans across the country participate in service projects in their communities to celebrate the legacy of civil rights leader Dr. Martin Luther King, Jr. The holiday honoring King will be observed on January 21, the day of the second inauguration of US President Barack Obama and Vice President Biden. JEWEL SAMAD/AFP/Getty Images

Chelsea Clinton (front L) departs after speaking as part of a National Day of Service event on the National Mall in Washington D.C. January 19, 2013. REUTERS/Eric Thayer

U.S. Vice President Joe Biden (C) embraces his wife Jill Biden after her remarks at a volunteer project to assemble care kits for U.S. military service members and veterans at a Unite America in Service event at the National Guard Armory in Washington, January 19, 2013. Biden and his family volunteered for the event during the National Day of Service as part of the 57th Presidential Inauguration. REUTERS/Jonathan Ernst