Constitutional referendums are important instruments at the end of numerous constitutional review processes. In recent years, these referendums are combined with deliberative instruments such as open forums, stakeholder conferences, and citizen assemblies. Constitutional referendums are also used in modern authoritarian regimes to strengthen the base of legitimacy of incumbent presidents. In the new Direct Democracy Integrity Index, experts evaluate the integrity in the different phases of the referendum cycle. In this index, citizen participation is one aspect in the pre-referendum phase. In this article, the Turkish constitutional referendum in 2017, and the Russian and Italian constitutional referendums in 2020 were analysed. The expert survey showed that referendums in the authoritarian regimes in Turkey and Russia have deficits of integrity in the pre-referendum phase. Authoritarian referendums often include symbolic outreach programmes and constitutional deliberation. But these crowdsourced constitutional processes are characterized by integrity insufficiencies. Nevertheless, the Italian referendum also lacks broad participatory instruments.