I think the whole "electability" conversation gives way too much credence to the predictions of these dip-**** pundits that so effectively demonstrated their worthlessness in 2016.
Keep in mind that the idea that a centrist has a better chance at winning isn't just because "This is what the pundits say". There have been studies done that show that moderate candidates do better than extremists at elections. (This doesn't mean that there aren't exceptions, and even a 'far left' candidate line Sanders does have a chance at defeating Trump... it would just mean Sanders would be bucking statistical trends.)
https://www.vox.com/2019/7/2/20677656/donald-trump-moderate-extremism-penalty
Now, I assume a lot of people are thinking "Trump was a right-wing extremist, and he won in 2016". But the thing is, that is actually wrong.
Now, I am not saying Trump was a good candidate. He is a liar, a con-man, and a racist. But, consider what he was campaigning on: He claimed he was against Iraq and Libyan military actions. (It was a lie, but that's still what he claimed). He said he would protect gay rights (even holding up an LGBTQ rainbow flag at a public event). He said because he was rich he knew tax loopholes and would be able to close them. (Which sounds a little like "get the rich to pay more".) He was going to bring in 'better health care' (even though he didn't actually have a plan for it). And he wasn't going to touch social security. Again, much of it was lies, but to a gullible person, he
sounded pretty moderate.
Compare him to other republican politicians at the time, folks like: Paul "privatize social securty" Ryan, or Rick "homosexuality is like beastiality" Santorum, or Ted "I'm voting against hurricane aid" Cruz. I would put Trump to the 'left' of the Republican party (according to his 2016 policies).
He can attack Trump's support because his policies speak directly and forcefully to the grievances of the stagnating working classes.
Except of course some of his policies seem to be rejected by that same working class.
Its all well and could to claim how those "working classes" will benefit under Sanders, but if those same people are rejecting your message right off the bat, you've certainly dug yourself into a hole early on.
Bernie has no "Wall Street speaking fees" scandal. He has no "my kid has do-nothing jobs related to industries I regulate" scandals. He has no "my criminal family is monetizing public service" scandal.
You're right, he doesn't have any of those scandals.
Instead, he has the "I stole from my neighbors" scandal. And the "I'll ship radioactive waste through minority communities" scandal (or, as the republicans will probably label it, "environmental racism".) And the "women enjoy rape don't they?" scandal (which, admittedly does have a reasonable explanation, but it will still be fodder for the republicans). And the "I went to a 'death-to-america rally' and all I got was this lousy T-shirt" scandal. And the "I honey-mooned in Moscow" scandal. And the "I called MYSELF a socialist" scandal.
https://thebulwark.com/this-is-how-trump-would-destroy-bernie-sanders/