They’ve actually done something quite clever with TUSC: basically, it’s just a franchise/brand, and anyone can stand as a TUSC candidate, as long as they agree with the platform approved by the steering committee, so they don’t need a network of branches or a top down bureaucracy.
Of course, this is classic front work, so, while they ostensibly aren’t in complete control of the situation, in practice they control all the co-ordinating levers. But it does point to a slightly different way of doing politics (though, I suspect, this is more like how US political parties operate, individuals and groups campaign under the brand umbrella, as compared to the European mass membership party model).