The products obtained during the early stages of the oxidative polymerization of aniline in the "falling pH" reaction were investigated using multinuclear solid-state magic-angle spinning (MAS) NMR combined with first-principles NMR chemical shielding calculations using the GIPAW (gauge-including projector augmented wave) method. A sample was synthesized starting from a 50:50 mixture of U-C-13 aniline and '5N-labeled aniline; two-dimensional C-13 refocused INADEQUATE, N-15-C-13 double CP, N-15 PDSD, and H-1-C-13/N-15 refocused INEPT MAS NMR spectra revealed the presence of quinoneimine structural units. Structural models that are consistent with the connectivities revealed by the C-13 refocused INADEQUATE and N-15-C-13 Double CP spectra are proposed. GIPAW chemical shift calculations are performed for model structures based on the proposed oligomeric structures; rioting that the model structures do not take into account intermolecular hydrogen bonding and CH-pi interactions, agreement and discrepancy to experiment are discussed.