The number of black and Hispanic registered voters has taken an enormous decline since four years ago and has the Obama campaign scrambling to sign up voters. The number of black voters dropped 7 percent, while Hispanic voters fell 5 percent, the first time it has dropped in almost 40 years. The decrease is being attributed to the struggling economy, which made it necessary for many to relocate in search of jobs. The strong turnout for Obama among the two groups is credited with helping him secure the presidency in 2008, and massive voter-registration pushes are starting across the country. That push is made more complicated by new legislation passed in eight states that require voters to show state-issued photo ID cards.