That poll is meaningless without listing “socialist party” as one of the options.
With a “socialist party” option, the Democrat support would fall to the teens, as most people who vote democrats are truly socialists.
Were the socialists chatting amongst themselves to start running their own candidates in a serious manner, it would make sense to factor them in separately. However, for them to try to split from the Dems would be silly, because they're "winning" at the moment. As it is now, the only possible split is on the right.