But Bernie staying positive and on message one could argue is what's helping him. If he buried Hillary early on, Maybe Biden jumps in and he's competing against a more liberal centrist which would be bad for him. Biden and Hillary both in the race would have been ideal for Bernie
No it wouldn't have been ideal.
Biden would have hurt Bernie more than anything. The race as it stands is Hillary vs. Maybe Bernie. It's her's to lose and she's been declining for a while. You forget she was up on Bernie by 50%+ at one point.
Biden is arguably just as liberal as Bernie (and more liberal than Hillary has been), just more electable since he's already vice president.
Biden would take votes away from Bernie, because of the fact he is more electable in the general. You forget Bernie is still a rather new phenomenon to casual voters in the last calendar year. Biden has been VP for 7 years so he's a household name.
Doesn't matter how much you believe the fairy tale that Biden in the race helps Bernie. He'd take votes away from Hillary voters, the ones who want a Dem to remain in the White House at any cost and establishment. And he'd take away some Bernie votes, the ones who aren't sold on Bernie's economic plan, but want a liberal in the white house again.
Bernie is benefitting right now from being "the other guy" in the race. People like options, which is why the Republican field always goes through cycles with different leaders or 2nd tier in the polls. If Biden were in the race it'd be Mrs. Bill Clinton vs. Mr. Vice President. Bernie would have been relegated to a Kucinich/Ron Paul outsider role. But since it's basically a two-horse race, Bernie gets the "I'm a Democrat, anybody but Hillary" vote. Where that vote would have been in favor of Biden because of his electability. And you know that Obama would endorse Biden because Biden would be the only one continuing his policies in the right direction.