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Comparative Government Unit 2: Political institutions

Countries organize executives, legislatures and courts differently, which shapes how power is checked.

Covers: Parliamentary, presidential and semi-presidential systems, executives, legislatures, judiciaries, term limits, checks on power

Study guide

In a parliamentary system, voters elect the legislature, and the leader of the majority party or coalition becomes prime minister. The executive and legislature are fused: the prime minister depends on parliament's confidence and can be removed by a vote of no confidence. The UK is the classic example, with a prime minister as head of government and the monarch as a ceremonial head of state. In a presidential system, the president is elected separately from the legislature, serves a fixed term and is both head of state and head of government, as in Mexico and Nigeria. A semi-presidential system has both a directly elected president and a prime minister; in Russia, the president holds most of the power.

Executives may face term limits. Mexico's president serves a single six-year term (sexenio), Nigeria's president can serve two four-year terms, and Russia changed its constitution in 2020 to allow Putin to stay in power longer. China removed presidential term limits in 2018. In Iran, the Supreme Leader, a cleric chosen by the Assembly of Experts, holds ultimate power over an elected president. China's real executive power lies with the general secretary of the Communist Party and the Politburo Standing Committee.

Legislatures can be unicameral (one house, like Iran's Majlis and China's National People's Congress) or bicameral (two houses, like the UK's House of Commons and House of Lords). Legislatures make laws, approve budgets and oversee the executive, but in authoritarian states they often rubber-stamp decisions. Courts differ too. Judicial independence means courts can rule without political pressure, and judicial review lets courts strike down laws. The UK has a Supreme Court (since 2009) but follows parliamentary sovereignty, so courts can't overturn acts of Parliament. Mexico and Nigeria have judicial review in theory, while in China and Iran courts serve the regime; Iran's Guardian Council vets laws and candidates for consistency with Islam.

Because the UK prime minister is whoever leads the majority party in the Commons, a party can replace its leader without a general election. In July 2026, Labour chose Andy Burnham after Keir Starmer resigned, and Burnham became prime minister. Earlier changes in power, such as Johnson to Truss to Sunak in 2022, also happened through internal party pressure, not votes of no confidence. Presidents are removed through impeachment, not confidence votes. In Nigeria, two-thirds of each chamber of the National Assembly must agree. Russia's process requires the Duma, the Federation Council and the courts and is nearly impossible in practice. Mexico also added a presidential recall referendum, first held in 2022, which López Obrador survived on low turnout. In Iran, the Assembly of Experts can in theory remove the Supreme Leader, and the Majlis can impeach ministers.

Russia's president nominates the prime minister, and the Duma must approve, though the president can dissolve the Duma if it refuses three times. China's premier is formally approved by the National People's Congress, but the Communist Party leadership picks the premier in advance. Russia's Federal Assembly has the State Duma (450 seats) and the Federation Council (two members per region). Mexico's Congress has a 500-seat Chamber of Deputies and a 128-seat Senate. Nigeria's National Assembly has a 109-seat Senate and a 360-seat House of Representatives. The UK House of Lords can only delay most bills, and a 2026 act removed its last hereditary peers.

Independent legislatures fight corruption through oversight. UK select committees question ministers, Mexico's Congress has been a real check since the PRI lost its majority in 1997, and Nigeria's National Assembly holds investigative hearings alongside the anticorruption agency EFCC. In China, Iran and Russia, legislatures rarely challenge the executive. A 2024 constitutional reform made Mexico's judges, including Supreme Court justices, popularly elected. The first judicial election was held in June 2025 with about 13% turnout, and the court shrank from 11 to 9 justices. Critics argue that Morena-aligned winners weakened judicial independence, while supporters say elections make judges accountable.

Authoritarian regimes keep courts weak so they cannot block the leader. Russia's courts rarely rule against the Kremlin, and its Constitutional Court approved the 2020 amendments. Nigeria's Supreme Court is more independent and regularly decides disputed elections, though corruption and delays undermine trust.

Key ideas

• Parliamentary systems fuse the executive and legislature.
• Presidential systems separate them with fixed terms.
• Russia's semi-presidential system gives the president most power.
• Iran's Supreme Leader and China's Communist Party hold ultimate power.
• Judicial independence and review vary greatly by country.

Formulas and rules

Common mistakes

• Thinking the UK monarch governs; the prime minister does.
• Assuming a constitution guaranteeing judicial review means courts are independent.

Words to know

Parliamentary system

Executive chosen by and accountable to the legislature.

Presidential system

Executive elected separately from the legislature for a fixed term.

Semi-presidential system

A system with both a president and a prime minister.

Head of state

The symbolic leader of a country.

Head of government

The leader who runs the government.

Vote of no confidence

A legislative vote that can remove a prime minister.

Coalition government

A government formed by multiple parties.

Sexenio

Mexico's single six-year presidential term.

Supreme Leader

Iran's top cleric and most powerful official.

Assembly of Experts

Iranian body that chooses the Supreme Leader.

Politburo Standing Committee

China's top decision-making body.

Unicameral

A legislature with one house.

Bicameral

A legislature with two houses.

House of Commons

The UK's elected and more powerful lower house.

Parliamentary sovereignty

Parliament's laws can't be overturned by courts.

Judicial independence

Courts' ability to rule free of political pressure.

Judicial review

Courts' power to strike down unconstitutional laws.

Guardian Council

Iranian body that vets candidates and laws for Islamic consistency.

Sample practice questions

5 more questions like these, from level 1 to 5, are in the practice set.