by-election

A by-election is an election held to fill a vacancy in a seat that has become vacant due to death, resignation, etc. It is different from a re-election, which is held to fill a lack of elected seats. A by-election is held when a vacancy cannot be filled by an early replacement and when a certain number of vacancies have been reached. In the case of members elected from a single-seat constituency in the House of Representatives, a by-election is held when one vacancy occurs, and in the case of members elected from proportional representation in the House of Representatives, a by-election is held when the total number of vacancies, including the number of elected seats missing, exceeds one-quarter of the total number of seats in the constituency in question. In the case of members elected from proportional representation in the House of Councillors, a by-election is held when the total number of vacancies, including the number of elected seats missing, exceeds one-quarter of the total number of seats in a regular election, and in the case of members elected from an electoral district in the House of Councillors, it is held when the total number of vacancies exceeds one-quarter of the total number of seats in a regular election in the constituency in question (Public Offices Election Act, Article 113, Paragraph 1, Items 1-4).

In the case of prefectural assembly members, a by-election is held when the number of vacancies, combined with the number of lacking elected seats in the same electoral district, reaches two or more (one in an electoral district with a single member quota), and in the case of municipal assembly members, when the number of vacancies, combined with the number of lacking elected seats, exceeds one-sixth of the number of seats in the electoral district (Public Offices Election Law, Article 113, Paragraph 1, Items 5 and 6). Even if the number of lacking seats does not reach these fixed numbers, a by-election (piggyback election) may be held for proportional representation members of the House of Councillors when an election for proportional representation members with different terms of office is held, for electoral district members of the House of Councillors when a re-election for electoral district members with the same terms of office or an election for electoral district members with different terms of office is held in that electoral district, and for local government members when another election for the same local government is held in that electoral district (Public Offices Election Law, Article 113, Paragraph 3).

A by-election shall be held within 40 days from the date on which the reason for holding the election arises for members of the House of Representatives and the House of Councillors, and within 50 days for members of local government assemblies (Article 34 of the same law). The term of office of a person who becomes a member through a by-election is the remaining term of his/her predecessor.

Generally, by-elections tend to have significantly lower voter turnout.

[Ryōshi Mitsuhashi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

死亡、辞職などにより議員の地位にある者に欠員を生じた場合、その欠員を補充するために行われる選挙。当選人の不足を補充するための再選挙とは異なる。補欠選挙は、繰り上げ補充によって欠員を補充できない場合に、しかも欠員が一定数に達したときに行われる。衆議院小選挙区選出議員の場合は、1人の欠員が生じたとき、衆議院比例代表選出議員の場合は、当選人の不足数と合算して当該選挙区における議員定数の4分の1を超える欠員が生じたときに行われる。また、参議院比例代表選出議員の場合は、当選人の不足数とあわせての欠員数合計が通常選挙における議員定数の4分の1を超えたとき、参議院選挙区選出議員の場合は、当該選挙区の通常選挙における議員定数の4分の1を超えたときである（公職選挙法113条1項1～4号）。

　都道府県議会議員の場合は、議員の欠員数が同一選挙区において当選人の不足数とあわせて2人以上（議員定数が1人の選挙区においては1人）に達したとき、市町村議会議員の場合には、議員の欠員数が当選人の不足数とあわせて当該選挙区における議員定数の6分の1を超えるに至ったときに補欠選挙が行われる（公職選挙法113条1項5・6号）。なお、議員の不足数がこれらの一定数に達しなくても、参議院比例代表選出議員の場合には、在任期間を異にする比例代表選出議員の選挙が行われるときに、参議院選挙区選出議員の場合には、その選挙区において在任期間を同じくする選挙区選出議員の再選挙または在任期間を異にする選挙区選出議員の選挙が行われるときに、地方公共団体の議員の場合には、その選挙区において同一の地方公共団体のほかの選挙が行われるときに、便乗による補欠選挙（便乗選挙）が行われる（同法113条3項）。

　補欠選挙は、選挙を行うべき事由が生じた日から、衆議院議員および参議院議員の場合については40日以内に、地方公共団体の議会議員の場合については50日以内に行われる（同法34条）。補欠選挙により議員となった者の任期は、前任者の残任期間である。

　一般に、補欠選挙の投票率は著しく低くなる傾向がみられる。

［三橋良士明］

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