Don't see the argument that Sanders isn't a stronger general election candidate. All it comes down to is he won't survive the Republican attack machine. If he's so fragile, why has he survived Hillary's attack machine? She has made the case he's unelectable and aggressively gone after him yet he still boasts higher favorables and better general election numbers.
Clinton can't attack him from the right effectively, since she needs left-of-center voters in the primaries. She's been attacking him from the left instead (guns, immigration, etc.) Obviously it's much more difficult to do that, than to paint Sanders as too pro-big government/will raise taxes for average Americans.
Hillary has attacked him from the right. She claimed that single payer is too expensive, and we just need incremental changes. Her surrogates attacked him for being a socialist. He's been attacked for "free stuff".
