“Mitt didn’t and he is sinking fast.”
Do you mean that Mitt didn’t talk about his own religion, or about Obama’s?
Anyway, my point is not that religious differences aren’t important in this election— especially in the primaries— but that making this seem like a holy war is very likely to backfire. The media loves to portray the GOP as being comprised exclusively of theocrats who want to disenfranchise all non-Christians. Why play into their hands, when we’ve got arguments that are as good if not better about Obama’s failure to lead economically?
Obama is going to try to make religion an issue in the general election campaign (anything to change the issue). He will try to paint a Santorum as intolerant and questioning Obama's faith. With Santorum that question is asked and answered, If Obama professes he is Christian then Santorum as a Christian is bound to believe him.
Mitt has yet to inoculate himself on the issue of his faith.