Even at the detriment of the candidate's chances in a general election, for the party faithful who decided the primary are very different from the swing voters who are crucial to the outcome of a general election. If Americans voted for persons and not for parties, the current contest would probably be one between John McCain and Bill Bradley. If it is law after the election, then it should be acceptable before it. The fact that so many potential voters don't vote, the fact that money is almost the decisive factor, the fact that not all Americans have an equal say in the primary process, the fact that the two big parties use their clout to exclude other candidates from the debates, and so on. These issues of real importance should be dealt with first.
Hypothetical problems can wait.
We cannot legislate for every single possible contingency that could ever occur, although I'm sure there are folks willing to try. This is not true. The rule that electoral votes determine the presidency exists because the framers wanted to balance the needs of the individual with the needs of each state. It is likely that there would be a lot of opposition to this idea by those concerned with state rights. Such opposition seems reasonable.