In the ending phase of the 2008 primary, during Hillary’s “hard working white Americans” period, like many Obama supporters, I felt like her campaign had devolved into a bunch of right-wing garbage that probably wasn’t needed. Others, like Paul Krugman disagreed, saying that the general election isn’t a friendly environment controlled by the Democratic party, so the primary doesn’t have to be either.
I was wrong, and those people were right. Obama was no Coakley and went about methodically defeating Hillary. Then he did the same thing to John McCain. (And later Willard Romney.)
The lesson is that if your candidate is so great, they will survive a real contested primary. If you aren’t sure and you care about winning the election, call on your own candidate to drop out, not the other ones.