Mitt Romney gets a kick out of South Dakota Sen. John Thune's comments during a January rally in Dubuque, Iowa. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

New Jersey Gov. Chris Christie greets Republican presidential candidate Mitt Romney in Des Moines, Iowa, on Dec. 30, 2011. Evan Vucci/AP hide caption

itoggle caption Evan Vucci/AP

Rep. Paul Ryan (left), R-Wis., and GOP presidential candidate Mitt Romney at a campaign stop in Appleton, Wis., on March 30. Steven Senne/AP hide caption

itoggle caption Steven Senne/AP

Former Arkansas Gov. Mike Huckabee delivers remarks to the Conservative Political Action Conference in February in Washington, D.C. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

Louisiana Gov. Bobby Jindal checks out damage off Grand Isle, La., from the Deepwater Horizon oil spill in June 2010. Spencer Platt/Getty Images hide caption

itoggle caption Spencer Platt/Getty Images

Former Minnesota Gov. Tim Pawlenty and GOP presidential candidate Mitt Romney campaign in Las Vegas on Oct. 17, 2011. Ethan Miller/Getty Images hide caption

itoggle caption Ethan Miller/Getty Images

Sen. Rob Portman, R-Ohio, campaigns with Mitt Romney in Cincinnati on Feb. 20. Mark Lyons/Getty Images hide caption

itoggle caption Mark Lyons/Getty Images