Kinetic simulation results reveal that the growth of the lower-hybrid drift instability (LHDI) in current sheets has an important effect on the onset and nonlinear development of magnetic reconnection. The LHDI does this by heating electrons anisotropically, by increasing the peak current density, by producing current bifurcation, and by causing ion velocity shear. The role of these in magnetic reconnection is explained. Confidence in the results is strongly enhanced by agreement between implicit and massively-parallel-explicit particle-in-cell simulations. (c) 2005 American Institute of Physics.