U.S. Republican presidential candidate and former Speaker of the House Gingrich is seen on a television screen on his campaign bus during a rally in The Villages, Florida

Republican presidential candidate Mitt Romney sits with his grandson Parker on his campaign bus enroute to a rally in Pompano Beach

Republican presidential candidate and former Massachusetts Governor Romney and his wife Ann walk to their campaign bus upon their arrival at the airport in Miami

Mitt Romney looks out through the window of his campaign bus as he leaves a campaign stop in Gilbert

A campaign bus carrying Republican presidential candidate Gingrich is seen at a campaign event in Columbia

Republican presidential candidate and former Massachusetts Governor Mitt Romney travels in his campaign bus, seen in the side view mirror of another vehicle, to a campaign stop in Ames

A bus belonging to Republican presidential candidate former House Speaker Newt Gingrich arrives at a campaign event in Dover

Republican presidential candidate Mitt Romney listens to a conference call on his bus enroute to a rally in Pompano Beach, Florida