If nothing else, a coronation would mean that she wouldn't be forced to develop a strong response to attacks relating to any weaknesses she has as a candidate until the GE which is dangerous. It really hurt Romney that the donors quickly made Gingerich shut up about Bain and Romney's taxes b/c it allowed Romney to just ignore the issue rather than developing a response to said attacks before Obama inevitably used them in the GE.
True. Another example would be the 2008 primaries, which helped Obama tremendously. Especially the "elitist" controversy, something that he got to address head on rather than just trying to shed that perception, like Kerry's hunting embarrassment.