“Winning Democratic primaries is not a qualification or a sign of who can win the general election. If it were, every nominee would win because every nominee wins Democratic primaries.”
Clutching at straws, getting weepy whenever you start trailing, this is not how you become electable. (is that even a word?) You become electable by, uh, winning elections. The Clinton camp seems to think that only she is strong enough to go up against McCain in November, but really, who couldn't beat Senator Hothead?
The primary reason for the presidential primaries is for each candidate to flaunt their appeal for voters. The voters listen to each candidate and measure what they have to say against what they have done in the past. They measure each candidate against the other then follow the one who seems to know where they are going.