User:KeithH/Mid-term vacancies in the United States Senate

Special election
Section 2 of the Seventeenth Amendment requires all mid-term vacancies to be filled by special election, with the winner of the special election taking office as soon as possible and serving until the original six-year term expires. However, the timing of special elections varies from state to state, with 13 states requiring such elections to happen as soon as possible after a vacancy, and 37 states (all of whom allow gubernatorial appointment) allowing the special election to happen concurrently with a regularly scheduled biennial congressional election.

In 18 states which allow gubernatorial appointment, if the vacancy occurs within a certain period of time before a scheduled biennial congressional election, the special election is scheduled for the following congressional election, meaning that an appointee may serve as long as 30 months before the special election.

Gubernatorial appointment
The Seventeenth Amendment also allows state legislatures to give the governor the power to appoint an interim senator who will serve until the special election is held. Forty-six states allow interim gubernatorial appointment in the event of a Senate vacancy. Oregon and Wisconsin specifically disallow the practice, while Oklahoma allows it in limited circumstances.

Four states (Arizona, Hawaii, Utah, and Wyoming) require that the appointee be of the same party as the previously elected incumbent. In three of these states (Hawaii, Utah, and Wyoming), the governor must choose the appointee from a list of nominees submitted by the previous incumbent's party.