The case is made here. Neil DeGrasse Tyson has said similar things in the past. I haven't thought much about it, but I'm somewhat skeptical if we're talking about the natural sciences. Certainly we need politicians with a deep appreciation of natural science, but I'm not sure we need natural scientists and engineers themselves. That smacks of technocracy and Thorstein Veblen's "soviet of technicians" to me.
I do think we would be much better off if the Congress were full of psychologists, sociologists, and economists (particularly the latter, of course!). Social science seems more directly relevant to a lot of what Congress does. A Congress informed by social science would know, after all, that most natural science and engineering relevant to what Congress does is the stuff of agents, not principals. Hire them, don't elect them.
But I still am somewhat leary of a Congress of social scientists. Democracy is about electing people you feel represent you, not about technocracy.
I guess what it boils down to is that I don't want a social scientist Congress... I want voters to want a social scientist Congress!