Wouldn't it have been a costless way to make Hillary and her partisans feel respected? I mean, she's already far-and-away the biggest draw of the night. I suspect most people think she's the keynoter anyway. The only difference is that, this way, her supporters would have had a nice symbolic trophy to tote around...
I guess the counter-argument is that Obama would look weak confering the honor on a vanquished rival. (But so much weaker than giving her a big prime time slot?) And maybe that trying to appease the Hillary dead-enders is a fool's errand, since nothing short of the nomination, or at least the veep nomination, would have done it.
--Noam Scheiber