Trapping of plasma electrons in the self-modulated laser wakefield accelerator via the coupling of Raman backscatter to the wake is examined analytically and with 3D test particle simulations. The trapping threshold for linear polarization is much less than for circular polarization and occurs for wake amplitudes of 25%, which is well below wave breaking. Self-channeling provides continuous focusing of the accelerated electrons, which, along with relativistic pump laser effects, can enhance the energy gain by a factor of $\ensuremath{\ge}2$.