One or two thoughts come to mind.
1. Obama dissed Hillary publically and in a big way, “And NOW he wants me to go out and do his dirty work? Screw him!”
2. Hillary is 100% sure Obama will lose so why tie her wagon to a plummeting rock?
3. If she goes out and makes inspiring speeches to the party faithful, it makes her look good, does nothing for Barack and sets her up to be her party’s primary spokesperson beyond the Presidential race.
What would Hillary say about Sarah? She doesn’t know how to fly on a broom!