The impending post-2026 delimitation exercise revived concerns over allocation of Lok Sabha (LS) seats among Indian states. Article 81 of the Constitution envisages representation proportional to population, with similar population–seat ratios across states. This posed few difficulties in 1951 or 1971. Subsequent decades witnessed sharp interstate divergence in population growth. States that achieved fertility decline & population stabilisation earlier now risk losing political influence relative to states with higher population growth. This paper argues that a purely population-based allocation formula is no longer adequate for preserving federal balance. It proposes a two-part approach: the existing allocation of 543 LS seats should remain unchanged. Additional seats created through LS expansion should be distributed based on a Demographic Performance (DemPer) principle derived from the logic of the 84th Constitutional Amendment, which recognised states’ population stabilisation efforts. The paper develops a DemPer framework based on states’ fertility transitions. It also creates scope for implementing women’s reservation through a hybrid First-Past-the-Post – Proportional Representation electoral mechanism.