Hot Air's Ed Morrissey thinks it's a big error not letting Palin speak because she could bring some much-needed passion to the proceedings.
Palin electrified the convention in 2008, and it’s just good manners to have the #2 from the last ticket speak at the next convention. Few people in the party can fire up the grassroots like Palin does, and few people will draw the attention she gets. If there is still room to offer her a speaking slot, the convention should do so, and do so quickly.

