The candidates and their families

Republican presidential candidate Mitt Romney greets Charlie Ryan and Janna Ryan, wife of newly announced Republican vice presidential candidate Rep. Paul Ryan, during a campaign rally in front of the USS Wisconsin August 11, 2012 in Norfolk, Va.

Malia Obama runs with Bo, followed by President Barack Obama and Sasha Obama, on the South Lawn of the White House Tuesday, April 14, 2009.

Republican Presidential candidate Mitt Romney stands with his wife, Ann Romney and grandchildren Nick Romney and Parker Romney during a campaign rally at Newark Town Square on June 17, 2012 in, Newark, Ohio.

Vice President Joe Biden, his wife Dr. Jill Biden and their family attend women's ice hockey preliminary game between United States and China at UBC Thunderbird Arena on February 14, 2010 in Vancouver, Canada.

Newly announced Republican vice presidential candidate, Wisconsin Rep. Paul Ryan, his family, and Republican presidential candidate Mitt Romney and his family, partially visible at center back, wave to the crowd Saturday, Aug. 11, 2012, in Norfolk, Va.

President Barack Obama, left, laughs with daughter Malia Obama as they watch the Olympic men's exhibition basketball game between Team USA and Brazil, Monday, July 16, 2012, in Washington.

Republican presidential candidate Mitt Romney holds his granddaughter Soleil Romney, 3, as he walks in the Wolfeboro Independence Day parade on July 4, 2012 in Wolfeboro, N.H.

Vice President-elect Joe Biden holds his granddaughter after President-elect Barack Obama gave his acceptance speech after it was announced he has won the presidential election at his election night rally in Chicago, November 4, 2008.

Janna Ryan, wife of newly announced Republican vice presidential candidate, Wisconsin Rep. Paul Ryan, partially visible behind her, greets crowd members after her husband addressed the crowd Saturday, Aug. 11, 2012 in Norfolk, Va.

First Lady Michelle Obama and daughters Malia and Sasha sing with Kermit the Frog during the 2011 National Christmas Tree Lighting Ceremony at the The Ellipse near the White House in Washington, D.C., on Dec. 1, 2011.

Republican presidential candidate Mitt Romney, his wife Ann Romney, his son Tagg Romney and some of his grandchildren wave to supporters during a campaign rally at the Raddisson Hotel April 24, 2012 in Manchester, N.H.

President-elect Barack Obama acknowledges the crowd, flanked by wife Michelle and daughters Sasha and Malia following his victory speech at his election party in Chicago, November 4, 2008.

Newly announced Republican vice presidential candidate, Rep. Paul Ryan, is hugged by his children as his wife Janna Ryan looks on after Republican presidential candidate Mitt Romney announced him as his running mate in front of the USS Wisconsin August 11, 2012 in Norfolk, Va.

From left, President Barack Obama, Sasha Obama, first lady Michelle Obama, Malia Obama and Michelle's mother Marian Robinson arrive at Chicago O'Hare International Airport on Air Force One, Friday, June 15, 2012.

Yoon S. Byun/The Boston Globe via Getty Images

Mitt Romney waves to the crowd - his wife Ann and son Tagg are at left. To his right are his grandchildren. GOP presidential candidate Mitt Romney speaks after the polls close on Super Tuesday at the Westin Copley Place in Boston, Mass. on Tuesday, March 6, 2012.

President Barack Obama walks with his daughters Malia (L) and Sasha behind the Easter bunny during the 134th annual Easter Egg Roll on the South Lawn of the White House April 9, 2012.

Ann Romney is flanked by family members as she introduces her husband, Republican presidential candidate Mitt Romney during an election party at the Red Rock Casino February 4, 2012 in Las Vegas.

Democratic vice presidential candidate Joe Biden walks off of the stage with his family after the vice presidential debate at the Field House of Washington University's Athletic Complex on October 2, 2008 in St. Louis.

Republican presidential candidate Mitt Romney greets family members as he arrives for an election party at the Red Rock Casino February 4, 2012 in Las Vegas.

Senate candidate Barack Obama, D-Ill., seated next to his wife, Michelle and their daughters Sasha, 3, far left and Malia, 6, wait for election returns in a Chicago hotel, Tuesday, Nov. 2, 2004.

Vice President Joe Biden and his granddaughter Naomi Biden exit from Air Force Two upon arrival at the Chinggis Khaan International Airport in Ulan Bator on August 22, 2011.

Republican presidential hopeful Mitt Romney disembarks from his campaign plane accompanied by some of his grandchildren prior to a campaign rally at Colorado Spring Fabrication in Colorado Springs, Colorado, February 4, 2012.

Vice President Joe Biden comes out of a plane with his wife Jill and granddaughter Finnegan, after landing at Vnukovo International Airport, outside Moscow on March 8, 2011.

Barack Obama, left, with his wife, Michelle, and daughter, Malia, delivers his concession speech after losing the Democratic primary in Illinois' 1st Congressional District — AP Photo/Frank Polich, File

In this March 21, 2000, file photo, Barack Obama, left, with his wife, Michelle, and daughter, Malia, delivers his concession speech after losing the Democratic primary in Illinois' 1st Congressional District.

Vice President Joe Biden, Mayor Michael Nutter of Philadelphia and Biden's granddaughter Natalie Biden observe the National Anthem before the game between D.C. United and the Philadelphia Union on April 10, 2010 at Lincoln Financial Field in Philadelphia

Republican presidential candidate Mitt Romney celebrates with his wife Ann and other family members during his Florida primary night party on January 31, 2012 in Tampa, Florida.

Republican presidential candidate Mitt Romney and his wife Ann listen to their grandson Parker greeting the crowd as their son Craig holds the microphone at Casa Marin restaurant in Hialeah, Fla., January 29, 2012.

President-elect Barack Obama and Vice President-elect Joe Biden are joined by Biden's mother, Jean, as they attend a victory rally in Chicago on November 4, 2008.