States differ in the extent to which they give their constitutions rigidity. Exploring constitutional amendment methods in 21 small island democracies with plurality elections, this study aims at explaining such rigidity differences. The leading expectation is that rigid amendment dominates in countries which have experienced in their political life disproportionate dominance in terms of party politics or excessive social fragmentation. These countries, namely, have probably internalized a need to ward off by means of high amendment thresholds sudden constitutional replacement, which is one possible consequence of the plurality election method. A main empirical finding is that a pattern of positive co-variance certainly exists. Whenever the triggering factors (dominance/fragmentation) are at hand, rigid amendment follows; whenever the factors are not at hand, moderate amendment follows. The finding strongly supports an image of small islands as thoughtful and purposeful political actors that design their political institutions to reflect their particular needs.