You've probably heard pundits point to various attributes of each presidential candidate — Obama's likeability or Romney's stance on the economy, for instance — as explanations of why they appeal with different demographics, or to explain rises and falls in the polls. A cheat sheet for November might answer the following questions: How much of a role will likeability play? Does it matter who's a flip flopper? Will voters care who is toughest on security? Or are we after who just seems more presidential? It could turn out that none of these factors make much of a difference.  John Casti  says it all boils down to mood. Casti is author of the book "Mood Matters: From Rising Skirt Lengths to the Collapse of World Powers"  and Director of the X Center, a research center for human-caused extreme events in Vienna.