Probably would have lost harder. Part of his enduring appeal is that he was able to create an image as some sort of crusader angel early on. Especially after the damn emails thing, everyone was like "Bernie is a good guy! Bernie is sticking to the issues!" and that's where the whole "I like Bernie's ideas and think he made a lot of great points this election but I really just think Hillary has the experience we need" thing came form. Around the start of the primaries in January and February, when people wanted to talk about the primaries with me, that was what they would all say, like they were reading off a script. Don't say anything bad about Bernie! He's the nice one!
Everyone is pouncing on him now that he's lost for the damn emails moment; they underestimate how much that helped him. It was really his first big national moment and it locked down his "positive campaign" image. So much so that now that he's slogging along with the most toxic campaign in history people still refuse to call a spade a spade because they've already committed to thinking of him as the positive guy.
The most toxic campaign in history, no way. Trump has that locked down by light years this cycle and as IceSpear mentioned, Wallace was pretty disgusting back in 1968. Nixon smearing McGovern was pretty nasty, and don't even get me started on either Bush