The biggest political scandal since Watergate, hence the name.
Said scandal occurred when Dubya paid an unannounced farewell visit to Baghdad. During a press conference an Iraqi journalist stood up and threw a pair of shoes at our President, one at a time. Using carefully honed Texan lightning reflexes, Dubya dodged the "shoe bombs" with a huge grin on his face. Hilarity ensued.
Sandalgate is also called "Shoe-icide attack" or "Bush's Boot Camp"