Iran stands at a critical juncture on the eve of snap presidential elections. Partly driven by the exclusion of most pro-reform candidates from national elections since 2020, the pattern of recent years has been declining voter turnout. The upcoming June 28 polls could represent a significant turning point.

Apart from a key indicator of public sentiment, turnout has long been a measure of legitimacy for the ruling political establishment. The 2020 parliamentary elections saw just over 42% of eligible voters cast...