It takes 270 electoral college votes to win come November.
Obama's campaign people have already figured they need Florida's electoral college points in order to win. So spinning the Martin shooting does at least two things:
1. Paints the Florida government/prosecuting attorney/DA folks as racist and incompetent
2. further fans the flames of racial and class warfare
There actually is a video of Obama's campaign person on YouTube describing about 4 "paths" Obama can get the necessary 270 votes. The first path he described was Florida.