I do not think that word means what you think it means (
49 million Democrats,
80 thousand DSAers)
I said "many", not "most". You are also conflating party registration for Dems with actual membership for DSA.
Let's look at elected officials. According to
wikipedia, there are 5 current DSA members in the Congress. That's ~2% of Congressional Dems. There are also several in Congress that used to be in the DSA but fell out with them.
There are also plenty of state legislators and even a few mayors.
They are also making a lot of noise. AOC is one of the most prominent Democrats of her generation and is an archetypal DSA Congresscritter.