[en] The parameter, P = N_pN_n/(N_p+N_n) is the number of valence protons (neutron) relative to the nearest shell or subshell closure, provides a simple and physically intuitive framework for understanding the evolution of collectivity in medium and heavy nuclei in terms of the competition between the spherical-driving, like-particle interaction and the deformation-driving, proton-neutron (p-n) interaction. In the past several years the P factor has been used to correlate a variety of properties of nuclear ground states and structures at low excitation energy. Here we present two new applications of this simple scheme: The isotopic systematics of 2₁⁺ states and the linearization of intruder 0+ states in the Pb region. The results show the versatility of the P-factor as a simple embodiment of the competition and balance between the p-n and pairing residual interactions that seem to determine much of the behavior of ground and excited configurations of medium and heavy nuclei