Sen. Marco Rubio, R-Fla., delivers a speech during the annual Conservative Political Action Conference in February in Washington. Win McNamee/Getty Images hide caption

itoggle caption Win McNamee/Getty Images

Republican presidential candidate Mitt Romney makes a pie shell with store owner Linda Hundt during a campaign stop Tuesday in DeWitt, Mich. Joe Raedle/Getty Images hide caption

itoggle caption Joe Raedle/Getty Images

President Obama meets with actor George Clooney, U.S. Special Envoy for Sudan Princeton N. Lyman, and human rights activist John Prendergast (far left) at the White House on March 15. Pete Souza/White House hide caption

itoggle caption Pete Souza/White House

An image from the Republican National Committee's Facebook page advertises its new "Social Victory Center" app. RNC via Facebook.com hide caption

itoggle caption RNC via Facebook.com