four-year mandate and can be reelected indefinitely, as set by the law. The election of mayors and councilmen takes place on the last Sunday of October and they take office on December 6 of that year. The last election was held on October 23, 2016 (moved from its original date of 30 October to avoid conflicting with a four-day holiday), and the next election is scheduled for October 25, 2020. Referendums National The Constitution provides for binding referendums (plebiscito) only in the case where a constitutional reform passed by Congress is completely vetoed by the President and then confirmed by Congress by a two-thirds majority of each chamber. In such an occurrence, the President has the authority to either sign the reform into law or call for a referendum. To date, the President has not exercised this power. Communal The Constitution allows municipalities to hold binding referendums to address various local issues. Referendums can be initiated by the mayor with council approval, by a two-thirds majority of council members, or by residents who represent 10% of the total voter turnout in the most recent municipal election. To date, only one such referendum has taken place. It was held in Peñalolén on December 11, 2011, and was used to determine a new zoning plan for the commune. Primaries Legal primaries There is a system of government-run primaries to select candidates for president, senator, deputy, and mayor. The primaries for president, senator, and deputy are held concurrently. Primaries can take place within a single political party or within a group of parties, known as a "pact." Independent candidates may participate in primaries with the backing of a political party or a pact. However, independents are not eligible to be candidates in primaries for congressional seats if the political party supporting the candidate is not part of a pact. Political parties may form separate pacts for presidential and parliamentary primaries. Political parties and pacts are free to decide whether to allow independent electors or electors affiliated with other political parties to participate in their primaries. However, independent electors must be allowed to vote in a presidential primary that includes an independent candidate. According to the Constitution, primary results are legally binding for political parties that use them. Candidates who lose in the primaries are ineligible to run for the same office in the general election, unless the winning candidate dies or resigns before