Why would he quit when his campaign has made more money than Hillary's lately (February numbers), and most of his contributions are coming from parts of the map that have yet to vote? That's absurd, not to mention insulting. Furthermore, dropping out would NOT help the democratic party. On the contrary, it garners interest in the process to continue it. Even if he does lose, it's not the right answer for EITHER campaign to call for him to pull out. He's not exactly slinging a lot of mud -- not nearly what's available anyway. He doesn't even -mention- the email thing, for instance.
Why don't Hillary-ites just realize that the reason that campaigns quit is because they run out of money, and he's not going to run out of money -- mainly due to the nature of his campaign financing strategy. It's not a bad thing. It's a good thing for BOTH candidates. Would the Superbowl winners somehow have an advantage if their opponent just quit at halftime as well?