In fairness "The Squad" is four people. It's hard to know to what extent the extreme left silliness has infected the party as a whole. The resurgence of Joe Biden suggests that maybe the hardcore left remain a minority, even if a large minority.
Okay. First, it should be noted that a number of members openly professing Socialism is a significant turn for the Democratic Party and would be for either of the big two parties. Until just recently, any suggestion of a Democrat being a Socialist was resisted with as much determination as if the accuser had said the candidate or officeholder was a Nazi. No more. The change is real and it has been reported by many observers that the Party's leadership is afraid of doing much of anything in public to resist the trend.
Not even Pelosi would do so much as to verbally reject the extremism of those Congresswomen through a simple Congressional resolution. Then too, a majority of the 17 or so candidates who were debating only weeks ago agreed with the Socialist policies espoused by Bernie and "The Squad," even while those candidates were posing as "Moderates." In sum, the evidence is there, and this development within the Democratic Party cannot be reduced to something as misleading as counting noses
("In fairness 'The Squad' is four people").
Second, this is why the Party's leadership has united behind the likes of Joe Biden. It's not because he's so compelling as a candidate; it's because that appears to be the only way to stop Sanders, given that the same Party strategists are afraid to just speak out against the Socialist inroads that have already been made by their extremists.