They aren’t, but popularity is their lifeblood. If their current candidates can’t win popular votes vs. these people running to to their left, they have to choose between becoming politically diminished in power and relevance or moving to the left.

It seems that they are scrambling now to find a way to avoid the consequences of their diminishing popularity without doing anything popular. They spent ages trying to get their “help the little guy” image polished up, but it has been so long since the little guy had a win that fewer and fewer people are buying it. It seems that when leftists are presented a choice between a liberal wearing a badge that says “leftist” and a leftist, they usually choose the leftist. In typical American fashion, rather than trying to beat their opponents, they’re trying to prevent opponents from existing.