From 21 May 2018 to 14 June 2018 the Czech Social Democratic Party (ČSSD) held a referendum to determine whether it should join the minority government of Andrej Babiš with potential confidence and supply from the Communist Party. 17,683 party members were eligible to vote and the referendum was deemed to be valid if the turnout reached at least 25%. A decision not to join the government would possibly trigger a snap election.