SCOOP

an analogy:

"Chess looks like a static sport, but it has a lot of ebbs and flows, just like a political campaign," says Bill Hall, executive director of the U.S. Chess Federation, the governing body of chess in the United States.

When you make a move on the board and it causes your opponent to retreat or divert his plan in order to respond to you, that is called gaining a tempo. Which Clinton did on March 4. But Obama has a "material advantage" (more pledged delegates), Hall says, which is like "having a better pawn structure" in chess. He also has a "space advantage," meaning he started out with a lead in Iowa and has kept it and the primary clock is winding down, leaving Clinton with few options.

"So she is getting squeezed out by his space advantage, and the only thing she can do is be fully in counterattack mode and regain the initiative in a big way and go for checkmate," says Hall. "In other words, she is on the edge of kind of a desperate situation. And when you get in a desperate situation, you're almost to the point of having an all-out attack because there are no draws in political campaigns."