Yeah...
Kerry resigns the nomination
No way Dems are going to let Pretty Boy be the nominee
Hillary comes on her white horse...
Its all in the cards.
Before the convention I would have agreed with you, but after the dims had their convention I don't think they can change their candiditate.
If I'm wrong someone correct me.
Jack
The DNC can change candidate at any time, up to the date the electors (not us, voters) cast their ballots in December.
What the DNC won't be able to easily do, and they may not care, is change the name of the presidential candidate on the voters ballot in each and every state. But naming the presidential candidate on the voters ballot is merely a convenience for voters. When the voter pulls a party lever, the voter's vote actually goes to an elector. Electors and their alternates have already been timely named by their respective parties.
As a practical matter, the DEM party wants to come up with a scenario that results in obtaining a majority of the electors' votes. But there is no legal impediment to changing the candidate -- even after the November election (it would be bizarre, but it is legal and possible).
See http://www4.law.cornell.edu/uscode/3/ch1.html <-- 3 USC 1
US Code, Title 3
CHAPTER 1 - PRESIDENTIAL ELECTIONS AND VACANCIES