In 2016, he was particularly involved in the 2016 constitutional referendum proposed by Renzi, where voters were asked whether they approve a constitutional law that amended the Italian Constitution to reform the composition and powers of the Parliament of Italy, as well as the division of powers between the State, the regions, and administrative entities. Landini campaigned for the "No", stating that it was a "badly made reform". On 4 December, the reform was reject by voters with 59% of votes against and 41% in favor, and Renzi resigned from his post.