4.2 Objectives of Election Rules

Proposals in 2026 to change how Mexico allocates its proportional representation seats did not pass Congress, so the mixed system of 300 district and 200 PR deputies is unchanged.

Since April 2026 no one sits in the UK House of Lords by inheritance, and in May 2026 Wales elected its Senedd by closed-list proportional representation for the first time (see 4.1).

• Control ballot access: who can register as a party or candidate.
• Make elections fair: independent bodies to run them and count votes.
• Shape the party system: thresholds that keep out small parties, or PR that lets them in.
• Widen representation: gender quotas, reserved seats or rules requiring national spread.
• Keep control: vetting candidates or appointing members instead of electing them.

Proportional representation usually brings more parties into the legislature and tends to elect more women and minority candidates. Single-member districts tend to favor two big parties, but every area gets its own representative, which strengthens constituency service and makes it clear whom to hold accountable.

Presidential rules that require a majority, as in Russia and Iran, or a spread of support, as in Nigeria, give the winner a claim to a national mandate. Changing any of these rules changes which religious, ethnic and economic groups win seats.

Timing differs too. The UK must hold a general election at least every five years but can hold one sooner; Mexico, Nigeria, Russia and Iran vote on fixed calendars set by their term lengths.

Gender quotas: Mexico has some of the world's strongest rules. A 2014 reform required parity in candidates for Congress, and a 2019 reform extended “parity in everything” to the cabinet, courts and state governments. Women now hold about half of the seats in both houses of Congress, and Mexico elected its first woman president in 2024. The UK has no legal quota, but a 2002 law lets parties use measures like all-women shortlists.

Reserved seats: Iran sets aside five Majles seats for recognized religious minorities.

National spread: Nigeria's 25% rule for presidents and requirements that parties be open to all Nigerians are meant to stop purely ethnic or regional parties. A 2018 law nicknamed “Not Too Young to Run” lowered the minimum age to run for president from 40 to 35 and for the House of Representatives from 30 to 25.

Appointed seats: members of the UK House of Lords are formally appointed by the monarch, mostly on the prime minister's advice, and an independent Appointments Commission vets nominees and recommends members with no party tie. Half of Iran's Guardian Council is chosen by the Supreme Leader and half is nominated by the head of the judiciary and approved by the Majles. Russia's Federation Council members are chosen by regional governors and legislatures. Some regimes use appointments to add expertise and a range of views; others use them to keep allies in place.