December 2015 polls had Bernie as the only candidate winning against Trump. But hey, the neolib establishment knows best!

Generic candidates always win. They have no flaws. No hang ups. No annoying habits. No awkward gafs. No history, no voting records. You can't even call him generic candidates. Because who people are voting for in that poll are more accurately they're idealized candidate. And by that I mean each individual person's idealized candidate. So of course they always win. When they put a name down the numbers change.