We investigate whether models based on the assumption that jets in quasars
are powered by rotating black holes can explain the observed radio dichotom
y of quasars. We show that in terms of the 'spin paradigm' models, radio-lo
ud quasars could be objects in which the rotation rate of the black hole co
rresponds to an equilibrium between spin-up by accretion and spin-down by t
he Blandford-Znajek mechanism. Radio-quiet quasars could be hosting black h
oles with an average spin much smaller than the equilibrium one. We discuss
possible accretion scenarios which can lead to such a bimodal distribution
of black hole spins.