So my candidate John Edwards is only doing a little better than my favored candidates usually do in an election. While it would take a miracle now for him to get the nomination, he could still be helpful in non-miraculous situations. The ideal situation is that his delegates at the convention decide whether Clinton or Obama gets the nomination, and Edwards endorses Obama in return for Obama fixing his health care proposal and a few other things. And even if that doesn't happen, a strong Edwards delegation can help push the party's platform in the right direction.
Because some smart people seem confused about this, voting for Edwards isn't a wasted vote if Obama is your second choice. Democratic primary delegates are awarded proportionately, so Clinton gets no more delegates on a 45-35-20 Clinton/Obama/Edwards vote split than with a 45-55 Clinton/Obama vote split (UPDATE: this is wrong for California - the candidate with a plurality gets extra delegates, I'm not sure how many. Strange how hard it is to get accurate info). She does get the psychological boost of coming in first, but I don't think that's reason enough to vote for the second-choice candidate.
Finally, at least in California, independents can vote in the Democratic primary. I think it's still possible to order the Democratic party ballot by mail, and independents can pick them up at the polls.
(And in case this seems really anti-Clinton: I surprised myself on reading this post, but in case the hypothetical crisis ocurred, Clinton would be my first choice (after Gore). But she'd only be my first choice by a hair, and other non-hypothetical issues are still more important.)