This article provides an in-depth analysis of the constitutional foundations and legislative framework of electoral rights for Spanish citizens residing abroad, taking as a starting point Art. 68, para. 5 of the Constitution of the Kingdom of Spain. Using a dogmatic-legal and historical method, the study examines the evolution of the subjective scope of the right (the interpretation of the phrase ‘being outside the territory of Spain’ and its extension from permanent to temporary residents) and its objective scope (the types of elections in which the diaspora can participate). The institution of ‘voto rogado’ is analyzed as a key case study illustrating the tension between the spirit of the constitution and legislative practice. Introduced in 2011 to prevent fraud, in practice it led to a drastic drop in voter turnout (from approx. 32% to below 5%), becoming a disproportionate barrier to exercising the right to vote. Consequently, following a broad political consensus, this system was abolished in 2022. The article concludes that the electoral law of Spaniards abroad is a dynamic category, and its real dimension is the result of a legislative compromise rather than merely a static constitutional guarantee, which offers a valuable lesson for other states.