Mechanisms for "charge-transfer" spontaneous polymerizations and cycloadditions between electron-rich olefins and electron-poor olefins were reviewed. As for propagation, literature proposals involving charge-transfer complexes were rejected. Instead, alternating copolymerization is ascribed to polar effects in free-radical reactions. As for spontaneous initiation, literature proposals involving charge-transfer complexes, with or without proton transfer, were rejected. Instead, the initiating species is postulated to be a tetramethylene zwitterion biradical, which may initiate either ionic homopolymerization or free-radical copolymerization. A new hypothesis proposes that any interaction that brings vinyl monomers close together may facilitate tetramethylene formation and spontaneous polymerization. These interactions include Coulombic, acid-base, hydrophobic-hydrophilic and templating-tethering interactions.