Why did he do it?
At a hastily arranged news conference, Crist said the right to vote is sacred and that "many have fought and died for this right." He said he consulted a leading Democratic legislator, Rep. Dan Gelber of Miami Beach, before issuing his order, and that Gelber knew of a similar order issued by Gov. Jeb Bush in 2002 that dealt with helping voters deal with new equipment. (Buzz audio here.)
As to the perception that more early voting helps Democrats, Crist said: "This is not a political decision. This is a people decision."
Kudos to Gov. Crist for actually putting country (or state) ahead of politics.