1. There is a speaking slot reserved for the VP.
2. No person could conceivably speak twice at the Democratic convention.
3. Thus, anyone already assigned to a speakers slot is ipso facto not going to be the VP nominee.
I call bullshit.
In the first place, I don't see any reason why someone couldn't speak twice. It would be a departure from what has been done in the past. So what?
But there's also a covert assumption here that strikes me as pretty implausible. That assumption is that the speaking schedule could not possibly be modified. But why couldn't it be? No reason that I can see.
As a matter of fact, it seems to me that the conventional wisdom has the significance of the schedule precisely backwards. When I look at the speaker's schedule, what it suggests to me is that the pick is likely to be Biden, Bayh, or maybe even Richardson. This is because all three are already set to speak on the same day the VP nominee address is scheduled. Which means, among other things, that moving any of them into the VP speaking slot wouldn't require much schedule shuffling.