If, suddenly, the Justice Department of a Democratic administration shattered that story with just days left before the convention, the negative momentum it would cause might make it tough for Clinton to recover. There would be doubts bordering on panic about What It All Means for Clinton going into the fall campaign, and she would have very little time to turn the story back in her favor.
Why does all of that matter? Because — as any Bernie Sanders supporter will tell you — Clinton doesn't have 2,383 pledged delegates: She has 2,220. This means she needs unpledged superdelegates to put her over the top. If there are major doubts about Clinton's ability to win in November, there could well be a major move of superdelegates away from her. But to whom?