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We investigate the helicity asymmetries and isospin ratios of radiative transition amplitudes for nucleon resonances electroproduced off proton and neutron targets at momentum transfers of ~' 5 3 G~v * .Calculations were done in the framework of a relativized constituent quark model which includes many-body effects due to the quark interaction potential and a consistent relativistic approximation of the center-of-mass motion of the three-quark system. We find significant deviations from the predictions of the nonrelativistic quark models and the SUI6) algebraic approach based on the single-quark-transition hypothesis. Our calculated relativistic corrections lead to an overall better agreement with the experimental data. The question of whether some of the low-lying P-wave baryons are of hybrid nature is briefly discussed. Finally we analyze the electroexcitation of the missing (20,1+ P-wave resonances.