I think Sanders could beat any of them, in theory. But it’s hard for me to see how some of the contestants, like Fiorina, could win the nomination let alone the general.
Sanders’s liability is supposed to be what, exactly? The lack of loyalty from the Democratic Party machine? The appearance of immoderation?
If he gets the nomination (and that may be the harder fight), what are Democratic Party bigshots going to do, wait four, maybe eight years for any patronage? Piffle.
As for his immoderate socialist identity. These days, political “moderation” seems kind of a joke, anyway. Some people (like Bernie Sanders himself) are good at compromising with those who disagree with them, while other “moderates” are really just persons whose opinions (however immoderate each opinion is) don’t match a stereotypical checklist.
But a Republican, probably any Republican contestant bar the non-pols (Carson, Trump, Fiorina) can be assumed to have embraced the Goldwater line that, “Extremism in the defense of liberty is no vice,” and to have a million other consciously and intentionally immoderate and extremist comrades to fill the government.
Bernie doesn’t have that, and that’s his advantage in a weird way. Sanders can’t build an administration entirely from the handful of independent socialdems in the country; he’ll have to appoint Democrats, some far more “moderate” than his own reputation.
So the nature of the Republican party moves any of its candidates toward pious immoderation, while the nature of the Democratic nomination moves Sanders toward a kind of moderation.
Is that too subtle?
OK, put it like this. Sanders may be an independent, but his politics are a lot closer than most pols to the policies of social liberal Democrats when those Democrats were winners: Truman, FDR, Hubert Humphrey, LBJ.
I think he can plausibly beat anyone the Republicans nominate. Not that he will, but he can.