A supermajority or supra-majority or a qualified majority, is a requirement for a proposal to gain a specified level of support which is greater than the threshold of more than one-half used for majority. Changes to constitutions, especially those with entrenched clauses, commonly require supermajority support in a legislature. Parliamentary procedure requires that any action of a deliberative assembly that may alter the rights of a minority have a supermajority requirement, such as a two-thirds vote.
Related concepts regarding alternatives to the majority vote requirement include a majority of the entire membership and a majority of the fixed membership. A supermajority can also be specified based on the entire membership or fixed membership rather than on those present and voting.
In the Democratic Party of the United States, the determination of a presidential nominee once required the votes of two-thirds of delegates to the Democratic National Convention. This rule was adopted in the party's first presidential nominating convention—the 1832 Democratic National Convention. The two-thirds rule gave southern Democrats an effective veto over any presidential nominee for many years, until the rule's abolition at the 1936 Democratic National Convention.
A majority vote, or more than half the votes cast, is a common voting basis. Instead of the basis of a majority, a supermajority can be specified using any fraction or percentage which is greater than one-half (i.e., 50%). It can also be called a qualified majority. Common supermajorities include three fifths (60%), two thirds (67%), and three quarters (75%).
A two-thirds vote, when unqualified, means two-thirds or more of the votes cast. This voting basis is equivalent to the number of votes in favor being at least twice the number of votes against. Abstentions and absences are excluded in calculating a two-thirds vote.
The two-thirds requirement can be qualified to include the entire membership of a body instead of only those present and voting, but such a requirement must be explicitly stated (such as "two-thirds of those members duly elected and sworn"). In this case, abstentions and absences count as votes against the proposal. Alternatively, the voting requirement could be specified as "two-thirds of those present", which has the effect of counting abstentions but not absences as votes against the proposal.
For example, if an organization has 150 members and at a meeting, 30 members are present with 25 votes cast, a "two-thirds vote" would be 17. If the requirement was "two-thirds of those present", that number would be 20. "Two-thirds of the entire membership" would be 100.
Another type of supermajority is three-fifths (60 percent). This requirement could also be qualified to include the entire membership or to include those present.
For the Montenegrin independence referendum held in 2006 the European Union envoy Miroslav Lajčák proposed independence if a 55% supermajority of votes are cast in favor with a minimum turnout of 50%. Such procedure, ultimately accepted by the government of Montenegro, was somewhat criticized as overriding the traditional practice of requiring a two-third supermajority, as practiced in all ex Yugoslav countries before (including the previous referendum in Montenegro).
Related concepts regarding alternatives to the majority vote requirement include a "majority of the entire membership" and a "majority of the fixed membership".
A majority of the entire membership is a voting basis that requires that more than half of all the members of a body (including those absent and those present but not voting) vote in favor of a proposition in order for it to be passed. In practical terms, it means an absence or an abstention from voting is equivalent to a "no" vote. It may be contrasted with a majority vote which only requires more than half of those actually voting to approve a proposition for it to be enacted. An absolute majority may also be the same as a majority of the entire membership, although this usage is not consistent.
In addition, a supermajority could be specified in this voting basis, such as a vote of "two-thirds of the entire membership".
By way of illustration, in February 2007 the Italian Government fell after it lost a vote in the Italian Senate by 158 votes to 136 (with 24 abstentions). The government needed an absolute majority in the 318 member house but fell two votes short of the required 160 when two of its own supporters abstained.
A majority of the fixed membership is based on the total number of the established fixed membership of the deliberative assembly. It is used only when a specific number of seats or memberships is established in the rules governing the organization.
A majority of the fixed membership would be different from a majority of the entire membership if there are vacancies.
For example, say a board has 12 seats. If the board has the maximum number of members, or 12 members, a majority of the entire membership and a majority of the fixed membership would be 7 members. However, if there are two vacancies (so that there are only 10 members on the board), then a majority of the entire membership would be 6 members (more than half of 10), but a majority of the fixed membership would still be 7 members.
It is possible for organizations that use a majority of the fixed membership to be caught in a stalemate if at least half the membership consists of vacancies, making it impossible to perform any actions until those vacancies are filled. The requirement for a minimum number of members to be present in order to conduct business, called a quorum, may be used to avoid such a possibility.
Similar to the voting basis for the entire membership, a supermajority could be specified for this basis, such as a vote of "two-thirds of the fixed membership".
Use in parliamentary procedure
This book also states:
Use in governments around the world
In Canada, most constitutional amendments can be passed only if identical resolutions are adopted by the House of Commons, the Senate and two thirds or more of the provincial legislative assemblies representing at least 50 percent of the national population.
Article 20 of the Constitution of Denmark states that if the government or parliament wants to cede parts of national sovereignty to an international body such as the European Union or the United Nations, it has to get a five-sixths majority in the Folketing (150 out of 179 seats). If there is only a simple majority, a referendum must be held on the subject.
The Council of the European Union uses 'Qualified majority voting' for the majority of issues brought before the institution. However, for matters of extreme importance for individual member states, unanimous voting is implemented. An example of this is Article 7 of the Treaty on European Union, whereby a member state can have its rights suspended with the unanimous approval of all other member states.
After the accession of Croatia, on 1 July 2013, at least 260 votes out of a total of 352 by at least 15 member states were required for legislation to be adopted by qualified majority. From 1 July 2013, the pass condition translated into:
Requirements to reach an absolute majority is a common feature of voting in the European Parliament (EP) where under the ordinary legislative procedure the EP is required to act by an absolute majority if it is to either amend or reject proposed legislation.
Article 368 of the Indian Constitution requires a supermajority of two-thirds of members present and voting in each house of Indian Parliament, subject to at least by a majority of the total membership of each House of Parliament, to amend the constitution. In addition, in matters affecting the states and judiciary, at least two thirds of all the states need to ratify the amendment.
The Rome Statute requires a seven-eighths majority of participating states to be amended.
The President of Italy is elected by an electoral college consisting of both chambers of Parliament sitting in joint session with 58 electors from the country's 20 regions. In the first three rounds of voting, a candidate must get two-thirds of the votes to win, but from the fourth round onwards only a simple majority is needed.
Under the Constitution of Nigeria a two-third majority is required in the National Assembly to alter the Constitution, enact legislation in a few areas, or remove office holders from some positions, such a Speaker. Legislative override or impeachment of the executive at either the state or federal government level also requires a two-thirds majority of the corresponding legislative assembly. 
Under the 1987 Constitution of the Philippines, a two-thirds majority of both houses of the Congress of the Philippines (the House and the Senate) meeting in joint session is required to declare war. A two-thirds majority of both Houses is required to override a presidential veto. A two-thirds vote of both chambers of Congress voting separately is required to designate the vice president as acting president in the event that a majority of the Cabinet certifies that the president is "unable to discharge the powers and duties of his office" but the president declares that no such inability exists. A two-thirds vote of either chamber is required to suspend or expel a member from that chamber.
Under the 1987 Constitution, "The Congress may, by a vote of two-thirds of all its Members, call a constitutional convention, or by a majority vote of all its Members, submit to the electorate the question of calling such a convention." A three-fourths vote of all the members of the Congress is required to propose an amendment to the Constitution; the proposed amendment is submitted to the people for ratification (by a majority of the votes cast) in a plebiscite.
A two-thirds majority of the Senate is required to ratify treaties, and to remove an impeached official from office. Impeachment by the House, which is the required first step in the removal process, only requires one-third of Representatives to sign a petition (specifically a verified complaint or resolution of impeachment).
The 1978 Constitution states that a three-fifths majority in both Congress of Deputies and Senate of Spain is needed to pass a constitutional reform, but if a two-thirds majority is reached in the Congress of Deputies, an absolute majority of senators is enough to pass the proposal.
Nevertheless, when a new Constitution is proposed or the proposal's goal is to reform the Preliminary Title, the Chapter on Fundamental Rights and Freedoms or the Title on the Crown, the supermajority becomes significantly harder:
- A supermajority of two-thids must be reached in both Congress of Deputies and Senate.
- Both chambers must be dissolved.
- The new elected chambers must approve the proposal by a new two-thirds supermajority.
- Finally, the proposal is passed by majority in referendum.
The first way has been used twice (1992 and 2011), but the second has been never used.
The Spanish Constitution states other supermajorities:
- Members of the General Council of the Judiciary are appointed by the Congress of Deputies and Senate of Spain, and each appointment needs a three-fifths majority.
- Members of the Constitutional Court are also appointed by both Congress of Deputies and Senate of Spain, and each appointment needs a three-fifths majority.
- The president of the RTVE, the public radio and television broadcaster, must be elected by two-thirds majority of the Congress of Deputies.
The Statute of Autonomy of the Canary Islands states that its economic and fiscal regime and electoral law need a two-thirds majority of the Parliament to be modified. On its behalf, the Ombudsman needs a three-fifths majority to be appointed. Also, if a two-thirds majority votes against a law project, it must be posposed to the following session.
Before the Additional Articles of the Constitution of the Republic of China in 2005, the constitution amendments need to be passed by the National Assembly. Since the Additional Articles ratified on June 7, 2005, the National Assembly is replaced by the Legislative Yuan. Amendments of the constitution need to be passed by three quarters of the members of Legislative Yuan, with more than half (50%) of voters hold referendums to approve the amendments.
The British House of Commons can be dissolved and an election held before the expiry of its 5-year term by a vote of two-thirds of the membership of the House of Commons since 2011 under the Fixed-term Parliaments Act 2011. This is the only supermajority required in the British Constitution. However, Parliament can also be dissolved if the House of Commons passes a motion of no-confidence in the government and no new government wins a motion of confidence within two weeks of the original vote of no-confidence.
A government with a majority that wanted to bypass the requirement for a two-thirds vote could pass an Act that stated, "Notwithstanding the Fixed-term Parliaments Act 2011, a general election will be called on DATE". It could also repeal the Act with a simple majority as well.
The United Nations Security Council requires a supermajority of the fixed membership on substantive matters (procedural matters require a simple majority of those present and voting). According to Article 27 of the United Nations Charter, at least nine of the Security Council's 15 members (i.e., a three-fifths supermajority) must vote in favor of a draft resolution in order to achieve passage. Specifying the fixed membership has the effect of making abstentions count as votes against—absences are not normal but would be treated the same way.
This is useful for the five permanent members of the Council (the United States, the Russian Federation, China, the United Kingdom, and France) because a vote against from any one of them constitutes a veto, which cannot be overridden. Permanent members who do not support a measure, but are unwilling to be seen to block it against the wishes of the majority of the Council, tend to abstain; abstentions by veto powers are generally seen by close observers of the UN as the equivalent of not vetoing votes against and have the same impact on the decision of the Security Council.
Amendments to the Constitution may be proposed in one of two ways: a two-thirds supermajority votes of each house of United States Congress or a convention called by Congress on application of two thirds (currently 34) of the states. Once proposed, the amendment must be ratified by three quarters (currently 38) of the states (either through the State legislatures, or ratification conventions, whichever "mode of ratification" Congress selects).
A treaty must be ratified by a two-thirds supermajority of the Senate to enter into force and effect.
Section 4 of the Twenty-fifth Amendment to the United States Constitution gives Congress a role to play in the event of a presidential disability. If the vice president and a majority of the president's cabinet declares that the president is unable to serve in that role, the vice president becomes acting president. Within 21 days of such a declaration (or, if Congress is in recess when a president is disabled, 21 days after Congress reconvenes), Congress must vote by two-thirds supermajorities to continue the disability declaration; otherwise, such declaration expires after the 21 days and the president would at that time "resume" discharging all of the powers and duties of the office. While Section 3 of this amendment (in which the president declares that they are unable to discharge the powers and duties of the Presidency) has been invoked three times, Section 4 has yet to be invoked.
The House may, by a simple majority vote, impeach a federal official (such as, but not limited to, the president, vice president, or a federal judge). Removal from office (and optional disqualification from any Federal, State or local office) requires a two-thirds supermajority of the Senate. In 1842, the House failed to impeach president John Tyler. In 1868, the Senate fell one vote short of removing president Andrew Johnson following his impeachment. In 1999, efforts to remove Bill Clinton following his impeachment in 1998 fell just short of a simple majority, and 17 votes short of the two-thirds supermajority. The impeachment procedure was last used in 2010, when Judge Thomas Porteous was removed from office. Each chamber may expel one of its own members by a two-thirds supermajority vote; this last happened when the House expelled James Traficant in 2002.
A two-thirds supermajority in the Senate is 67 out of 100 senators, while a two-thirds supermajority in the House is 290 out of 435 representatives. However, since many votes take place without every seat in the House filled and representative participating, it does not often require 67 senators or 290 representatives to achieve this supermajority.
Apart from these constitutional requirements, a Senate rule (except in cases covered by the nuclear option, or of a rule change) requires an absolute supermajority of three fifths to move to a vote through a cloture motion, which closes debate on a bill or nomination, thus ending a filibuster by a minority of members. In current practice, the mere threat of a filibuster prevents passing almost any measure that has less than three-fifths agreement in the Senate, 60 of the 100 senators if every seat is filled.
For state legislatures in the United States, Mason's Manual says, "A deliberative body cannot by its own act or rule require a two-thirds vote to take any action where the constitution or controlling authority requires only a majority vote. To require a two-thirds vote, for example, to take any action would be to give to any number more than one-third of the members the power to defeat the action and amount to a delegation of the powers of the body to a minority." Some states require a supermajority for passage of a constitutional amendment or statutory initiative.
Many state constitutions allow or require amendments to their own constitutions to be proposed by supermajorities of the state legislature; these amendments must usually be approved by the voters at one or more subsequent elections. Michigan, for instance, allows the Legislature to propose an amendment to the Michigan Constitution; it must then be ratified by the voters at the next general election (unless a special election is called).
In most states, the state legislature may override a governor's veto of legislation. In most states, a two-thirds supermajority of both chambers is required. However, in some states (e.g., Illinois, Maryland and North Carolina), only a three-fifths supermajority is required, while in West Virginia only a normal majority is needed.
One common provision of so-called "taxpayer bill of rights" laws (either in state statutes or state constitutions) is requirement of a supermajority vote in the state legislature to increase taxes. The National Conference of State Legislatures reported in 2010 that fifteen states required a supermajority vote (either a three-fifths, two-thirds or three-fourths majority vote in both chambers) to pass some or all tax increases.
Supermajority requirements for tax increases have been criticized as "deeply flawed" by a report by the progressive Center on Budget and Policy Priorities because such requirements empower a minority of legislators, making it difficult to close tax loopholes or fund transportation infrastructure, and also may encourage pork-barrel spending as a trade-off to ensure passage of a tax increase (see logrolling).