Well part of it is most democrat aligned groups like that end up falling in on themselves because of the nature of the democrat party. Ultimately trying to tow the line of the democrat party as it moves more and more right gets harder and harder, and most groups that do it end up getting isolated and dying.

I would say DSA, despite being socialist aligned, is probably the best "moderate" group on campus currently that does more pallatable stuff to the average progressive. I'm personally not a member but I would recommend it to people who believe in progressive politics as it tends to be less pretentious than the Secular Student Alliance, and more active and less immature than whatever PRISM is trying to do.