That's OK, because if it turns out that he doesn't win the primary, Senator Obama plans to donate all of his remaining campaign funds to whoever is the Democratic party nominee. So your donation will not only help to restore hope, it will help ensure that the eventual Democratic nominee is elected.
First of all, does that work on anybody? I'm sure any losing candidate who has leftover campaign funds will donate them to other Democrats, quite possibly the presidential candidate, or else their own campaign for senate or governor or whatever. So if I want to support the Democrats, why wouldn't I give my money to the one I actually hope is the nominee? That's the worst logic I've ever heard to donate money to a candidate who isn't my first choice.
Secondly, I wonder how the millions of people who actually support Barack Obama would feel knowing that their candidate's sales pitch is: "Give money to me. If I don't use it, I'll pass it onto Hillary Clinton." He certainly hasn't announced that publicly before as far as I know.
Ironically, I think the only way anyone could convince me to donate to Obama at this point would be if he gave up on his policy of eschewing negative campaigning and convinced me that donating to him is the most effective way to stop Hillary Clinton from winning the nomination.