“We consider the economy fundamental, or foundational, to presidential election outcomes,” write John Sides and Lynn Vavreck in The Gamble: Choice and Chance in the 2012 Presidential Election .. http://www.amazon.com/dp/0691163634/?tag=slatmaga-20 . There’s an almost linear relationship between economic growth and political success: If an incumbent party has growth, it wins; if it doesn’t, it loses. Yes, this is mediated by other variables, from foreign conflicts to tenure in office. But the overall pattern holds.