If Sanders were going to outperform Clinton in the general, he would be doing so in the primary.
I've seen a lot of people claiming that Sanders would be more likely than Clinton to win the general election.
Almost exclusively, those people also believed that Sanders was going to win the primary, which should cast some doubt on their judgement, although some of them are now beginning to acknowledge that it is looking unlikely. But there's another, more important, reason not to accept that claim (actually, there are lots, but here's one: )
The narrative behind Bernie Sanders' claim to electability is that he can energise people, especially among the young, who want a more passionately left-wing government. He says that there are a lot of such people - enough to constitute a revolution - who have not voted in large numbers in the past, but would do for him.
The thing is that if this phenomenon were real, its effect would be more noticeable in the primary - where turnout is much lower, and left-wing views more widespread - than it will be in the general.
The primary electorate is more favourable to Sanders compared to Clinton than the general electorate will be. So if he has won the primary, it would not necessarily have proven that he were more electable (although it would be circumstantial evidence that he might be), but when she does, it will conclusively demonstrate that she is.
If Clinton can beat Sanders in the primary with a message tailored less specifically for the primary electorate, and more generally for the country as a whole, than his, it will prove that she is the candidate more likely to win the general.
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to the steps of the oligarchy!
Love the graphic. 
Despite the *fact* that Bernie draws republicans, not only in his home state but in matchups.
That's assuming a lot, especially considering how well Bernie does in matchup polls. 
