This combination of file pictures shows Republican presidential candidate Mitt Romney (L) speaking during an address to the 39th Conservative Political Action Committee February 10, 2012 in Washington, DC. , and US President Barack Obama (R) speaking during a campaign event at Prime Osborn Convention Center July 19, 2012 in Jacksonville, Florida. AFP PHOTO/Mandel NGAN

This combination of file pictures shows US President Barack Obama (L) speaking during a campaign event at the Apollo Theatre in New York on January 19, 2012, and Republican presidential candidate Mitt Romney (R) smiling as he arrives to speaks at his caucus night rally following republican caucuses in Des Moines, Iowa, on January 3, 2012. AFP Photo/Jewel Samad

This combination of file pictures shows US Republican presidential candidate Mitt Romney (L) speaking during a campaign event with coal miners at the American Energy Corporation in Beallsville, Ohio, August 14, 2012, and US President Barack Obama (R) speaking during a Labor Day campaign event September 3, 2012 at Scott High School in Toledo, Ohio. AFP PHOTO / Saul LOEB /Mandel NGAN

This combination of file pictures shows US Republican presidential candidate Mitt Romney (R) speaking at the American Legion national convention in Indianapois, Indiana, on August 29, 2012, and US President Barack Obama (L) speaks during a campaign rally at Mentor High School in Mentor, Ohio, on November 3, 2012. Republican challenger Mitt Romney will make a last-minute play for Pennsylvania NOvember 4, 2012 as he and President Barack Obama criss-cross America in a final push for votes on the penultimate day of their tense White House campaign. AFP PHOTO /Jewel Samad

US President Barack Obama greets Republican presidential candidate Mitt Romney following the third and final presidential debate at Lynn University in Boca Raton, Florida, on October 22, 2012. The showdown focusing on foreign policy is being held in the critical toss-up state of Florida just 15 days before the election and promises to be among the most watched 90 minutes of the entire 2012 campaign. AFP PHOTO/Jewel Samad

US President Barack Obama (R) greets Republican presidential candidate Mitt Romney (L) following the third and final presidential debate at Lynn University in Boca Raton, Florida, October 22, 2012. The showdown focusing on foreign policy is being held in the crucial toss-up state of Florida just 15 days before the election and promises to be among the most watched 90 minutes of the entire 2012 campaign. AFP PHOTO / Saul LOEB

US President Barack Obama (R) and Republican presidential candidate Mitt Romney greet each other before the third and final presidential debate at Lynn University in Boca Raton, Florida, on October 22, 2012. The showdown focusing on foreign policy is being held in the critical toss-up state of Florida just 15 days before the election and promises to be among the most watched 90 minutes of the entire 2012 campaign. AFP PHOTO / Jewel SAMAD

US President Barack Obama and Republican Presidential candidate Mitt Romney participate in the third and final presidential debate at Lynn University in Boca Raton, Florida, October 22, 2012. AFP PHOTO/Emmanuel DUNAND

US President Barack Obama (R) shakes hands with Republican presidential candidate Mitt Romney at the end of the third and final presidential debate at Lynn University in Boca Raton, Florida, on October 22, 2012. The showdown focusing on foreign policy is being held in the critical toss-up state of Florida just 15 days before the election and promises to be among the most watched 90 minutes of the entire 2012 campaign.AFP PHOTO/Jewel Samad

US President Barack Obama (R) and Republican presidential candidate Mitt Romney share a laugh at the end of the third and final presidential debate at Lynn University in Boca Raton, Florida, on October 22, 2012. The showdown focusing on foreign policy is being held in the critical toss-up state of Florida just 15 days before the election and promises to be among the most watched 90 minutes of the entire 2012 campaign. AFP PHOTO / Saul LOEB

US President Barack Obama shakes hands with Republican presidential candidate Mitt Romney at the end of the third and final presidential debate October 22, 2012 at Lynn University in Boca Raton, Florida. AFP PHOTO/Mandel NGAN

US President Barack Obama Republican presidential candidate Mitt Romney make their way to greet their wives at the end of the third and final presidential debate October 22, 2012 at Lynn University in Boca Raton, Florida. AFP PHOTO/Mandel NGAN

This combination of file pictures shows (L) supporters cheering US President Barack Obama after he accepted the Democratic National Convention's nomination to run for a second term as president at the Time Warner Cable Arena in Charlotte, North Carolina, on September 6, 2012 on the final day of the DNC, and (R) Republican presidential candidate Mitt Romney and vice presidential nominee Paul Ryan welcoming their families onto the stage following Romney's acceptance speech at the Tampa Bay Times Forum in Tampa, Florida, on August 30, 2012 on the final day of the Republican National Convention (RNC). AFP PHOTO Stan HONDA

This combination of file pictures shows (L) supporters waving banners reading "Forward" as US President Barack Obama states his acceptance to run for a second term as president at the Time Warner Cable Arena in Charlotte, North Carolina, on September 6, 2012 on the final day of the Democratic National Convention (DNC), and (R) delegates waving banners during the Republican presidential candidate Mitt Romney's acceptance speech at the Tampa Bay Times Forum in Tampa, Florida, on August 30, 2012 on the final day of the Republican National Convention (RNC). AFP PHOTO/ Brendan SMIALOWSKI / Mladen ANTONOV

This combination of file pictures shows (L) an official White House photographs showing US President Barack Obama and his daughters, Malia (L) and Sasha watching on television in the Treaty Room of the White House on September 4, 2012, as US First Lady Michelle Obama takes the stage to deliver her speech at the Democratic National Convention in Charlotte, North Carolina, and (R) US Republican presidential candidate Mitt Romney along with his grandchildren watching the Republican National Convention on television in their hotel room in Tampa, Florida, on August 29, 2012. AFP PHOTO / Official White House Photograph/Pete Souza -Jewel Samad/AFP

This combination of file pictures shows US President Barack Obama (L) arriving at Andrews Air Force Base to board Air Force One on March 16, 2012 in Maryland, and US Republican presidential candidate Mitt Romney (R) arriving to board his campaign plane at Lea County Regional Airport in Hobbs, New Mexico, on August 23, 2012. AFP PHOTO/Brendan SMIALOWSKI /Jewel Samad

This combination of files pictures shows (L) US President Barack Obama and First Lady Michelle Obama chating as they walk to the White House in Washington, DC, on December 14, 2011, and (R) US Republican presidential candidate Mitt Romney and his wife Ann leaving the Church of Jesus Christ of Latter-Day Saints in Wolfeboro, New Hampshire, after Sunday services on August 26, 2012. AFP PHOTO/Jewel Samad

This combination of file pictures shows Republican presidential hopeful Mitt Romney (L) holding a campaign rally at Colorado Spring Fabrication in Colorado Springs, Colorado, February 4, 2012, and US President Barack Obama speaking about job creation and the economy at the International Brotherhood of Electrical Workers (IBEW) Local No. 5 Training Center in Pittsburgh, Pennsylvania, October 11, 2011. AFP PHOTO/Emmanuel Dunand / Saul LOEB

This combination of file pictures shows T-shirts bearing the image of Republican presidential candidate Mitt Romney (L) and the image of US President Barack Obama (R) for sale at a retail shop inside Dulles International Airport near Washington, DC, September 17, 2012 in Chantilly, Virginia. AFP Photo/Paul J. Richards

This combination of file pictures shows (L) US president-elect Barack Obama and his wife Michelle embracing on stage during Obama's election night victory rally at Grant Park on November 4, 2008 in Chicago, Illinois, and (R) former Massachusetts Governor Mitt Romney kissing his wife Ann after the first 2012 Republican presidential candidates' debate in Manchester, New Hampshire June 13, 2011. AFP PHOTO / Emmanuel DUNAND