The evolution of the correlated two-electron eigenmodes of the negative potassium ion K^- is followed as a function of the system's root mean square size R with the aid of the hyperspherical potential curves and relief plots of the corresponding density distributions. Lee's (1975) multichannel reaction matrix theory formulated originally for Cs^- is reviewed for the analogous system K^-. The authors verify numerically Lee's assumption that the ejection of an electron from the region of strong exchange interaction to the jj-coupled detachment zone is sudden.