So "the Democratic base" who voted for Clinton are going to refuse to vote for Obama if he is the candidate adopted by the party? Even though you can guarantee that Clinton is going to be campaigning for him? Doesn't seem too likely.

Whereas the opposite scenario, in which people who aren't part of that "Democratic base" but who came out to vote for Obama refuse to vote for Clinton, if she is adopted, doesn't seem at all unlikely. Even though you can guarantee that Obama will be campaigning for her.