A constitutional referendum was held in Ghana on 31 January 1964. The proposed amendments to the constitution would turn the country into a one-party state and increase the powers of President Kwame Nkrumah. With results showing that an implausible 99.91% of voters supported the amendments, the referendum was accused of being "obviously rigged".
Ghanaian constitutional referendum, 1964 Wikipedia
Following the successful passage of the constitutional amendments, the country became a one-party state, with the Convention People's Party as the sole legal party (though the country had essentially been a one-party state since independence in 1957). Nkrumah became president for life of both nation and party, with greatly expanded powers. For instance, he could now remove members of the Supreme Court at his discretion. In effect, the amendments transformed Nkrumah's regime into a legal dictatorship. Elections were scheduled to be held under this system in 1965, but were cancelled shortly beforehand, with Nkrumah appointing MPs instead. However, Nkrumah was overthrown in a coup in February 1966, the CPP was dissolved, and the constitution suspended. Multi-party politics was restored by the time of the next elections in 1969.