It has a trickle down effect
I do not doubt that Obama's highly irrational campaign activated many of these stunted people. But it did not begin with him.
One fundamental expression of the liberal mind is an infantile wish to be reunited with Mommy. Nirvana, the ultimate dissolution of the indiviudal, merged with everyone else. You see it in the "commune" impulse noted by others above. You see it in the iconic "Kumbaya." "We are the world." "I'd like to teach the world to sing." On and on it goes.
On the macro scale, it is seen in the intensely pathological "One World" impulse, It is made real by the traumatized Europeans, huddling together in the EU, hoping that by shacking up they will finally keep from killing each other. On and on it goes.
It is driven by the fear of separation and abandonment, which normal people resolve by the age of about six, and who go on to become adults and political conservatives.
In this case, we should call it the dribble down effect.