I wouldn't worry too much about any polls running generic Democrat candidates, whether they're being run against a real person or not. People have brand loyalty. Would you rather buy an American car or a Japanese car? Most Americans would choose the former as a general rule, but somehow when it comes to specifics, they end up buying a lot of Toyotas, once they get around to comparing actual models.
I'm not reading any articles that say "I'm amazed that I've become a liberal," or "I never thought I'd vote for a Democrat," but you see a lot the other way around. People still think of themselves as "mostly Democrat," but once the nominee starts talking they start wondering whether this is Another Time To Make An Exception.