Doug Jones won election from an overwhelmingly conservative state despite having liberal views on abortion that would normally cause the chattering classes to proclaim him “unelectable” there. And his other views tend to the left end of the political spectrum (by Alabama standards, anyhow) as well.
Yes, of course Jones won because Roy Moore was a tragically flawed candidate. Of course that means a non-tragically-flawed, garden-variety Republican would have mopped the floor with Jones. But a garden-variety Republican wasn’t running against Jones. Moore was.
Likewise, Sanders wouldn’t have been running against a garden-variety Republican, either. He would have been running against deeply flawed, faux populist Trump. Sanders’ genuine (or at least more genuine by far than Trump’s) populism would have enabled him to mop the floor with Trump in the debates.
Yes, Trump would have played dirty and tried to paint Sanders as an unrequited Stalinist. It probably wouldn’t have worked. Vermont is far less thoroughly liberal than most give that state credit for (it currently has a Republican governor, and for a long time its other, non-Sanders senator was a Republican).
Yet Sanders’ rhetoric has managed to successfully sell himself to many who don’t generally identify as leftists. Plus Sanders’ own experience selling himself to such voters would have led him to campaign seriously in swing states and normally Republican-leaning areas that Hillary Clinton decided weren’t worth wasting her time on. That in turn would have stopped certain key states from swinging to Trump.
One of the biggest errors politically moderate pundits make is assuming that because they, personally, happen to be highly ideological people, everyone else is, too. (Adhering to political moderation is as ideological a behavior as is adhering to any other political ideology.)
I do not believe the describes most swing voters, who are what I call “non-ideological pragmatists.” They’re not tightly committed to the left, right, or the center; they’re more focused on individual candidates and their messages than they are on any ideology. If a candidate does a good, convincing job of explaining him or herself, these pragmatists tend to be seriously willing to give him or her a try. It’s a huge part of the reason Ronald Reagan (who wasn’t labeled “The Great Communicator” for nothing) was so successful.
Bernie Sanders is another of those great communicators and as a such would have had a real chance, particularly when you figure in the high negatives of his opponent.