United States Senate

====Vacancies====
The [[Seventeenth Amendment to the United States Constitution|Seventeenth Amendment]] requires that vacancies in the Senate be filled by special election. Whenever a senator must be appointed or elected, the [[secretary of the Senate]] mails one of three forms to the state's governor to inform them of the proper wording to certify the appointment of a new senator.<ref>{{Cite web |title=The Term of A Senator – When Does It Begin and End? – Senate 98-29 |url=https://www.senate.gov/reference/resources/pdf/termofasenator.pdf |url-status=live |archive-url=https://web.archive.org/web/20201222214934/https://www.senate.gov/reference/resources/pdf/termofasenator.pdf |archive-date=December 22, 2020 |access-date=November 13, 2015 |website=United States Senate |publisher=United States Printing Office |pages=14–15}}</ref> If a special election for one seat happens to coincide with a general election for the state's other seat, each seat is contested separately. A senator elected in a special election takes office as soon as possible after the election and serves until the original six-year term expires (i.e. not for a full-term).

The Seventeenth Amendment permits state legislatures to empower their governors to make temporary appointments until the required special election takes place.

The manner by which the Seventeenth Amendment is enacted varies among the states. A 2018 report breaks this down into the following three broad categories (specific procedures vary among the states):<ref name="CRS_R44781">{{Cite web |last=Neale |first=Thomas H. |date=April 12, 2018 |title=U.S. Senate Vacancies: Contemporary Developments and Perspectives |url=https://fas.org/sgp/crs/misc/R44781.pdf |url-status=live |archive-url=https://web.archive.org/web/20180605230617/https://fas.org/sgp/crs/misc/R44781.pdf |archive-date=June 5, 2018 |access-date=October 13, 2018 |website=fas.org |publisher=Congressional Research Service}} '''NOTE:''' wherever present, references to page numbers in superscripts refer to the electronic (.pdf) pagination, not as found printed on the bottom margin of displayed pages.</ref>
* Four states – [[North Dakota]], [[Oregon]], [[Rhode Island]], and [[Wisconsin]] – do not empower their governors to make temporary appointments, relying exclusively on the required special election provision in the Seventeenth Amendment.<ref name="CRS_R44781" />{{rp|7–8}}
* Eight states – [[Alaska]], [[Connecticut]], [[Louisiana]], [[Massachusetts]], [[Mississippi]], [[Texas]], [[Vermont]], and [[Washington (state)|Washington]] – provide for gubernatorial appointments, but also require a special election on an accelerated schedule.<ref name="CRS_R44781" />{{rp|10–11}}
* The remaining thirty-eight states provide for gubernatorial appointments, "with the appointed senator serving the balance of the term or until the next statewide general election".<ref name="CRS_R44781" />{{rp|8–9}}

In ten states within the final category above – [[Arizona]], [[Hawaii]], [[Kentucky]],<ref>{{cite web|url=https://www.courier-journal.com/story/news/politics/ky-general-assembly/2021/03/29/kentucky-lawmakers-nix-veto-mcconnell-backed-senate-vacancy-plan/7055091002/|title=Kentucky lawmakers override veto of Mitch McConnell-backed Senate vacancy plan|author=Morgan Watkins|publisher=Louisville Courier Journal|access-date=September 2, 2023}}</ref> [[Maryland]], [[Montana]], [[North Carolina]], [[Oklahoma]], [[Utah]], [[West Virginia]], and [[Wyoming]] – the governor must appoint someone of the same political party as the previous incumbent.<ref name="CRS_R44781" />{{rp|9}}<ref name=OCPA>{{cite news |title=House approves appointment process for U.S. Senate vacancies |url=https://www.ocpathink.org/post/house-approves-appointment-process-for-u-s-senate-vacancies |work=OCPA |publisher=Oklahoma Council of Public Affairs |date=May 27, 2021 |access-date=December 21, 2022 |archive-date=February 13, 2023 |archive-url=https://web.archive.org/web/20230213095954/https://www.ocpathink.org/post/house-approves-appointment-process-for-u-s-senate-vacancies |url-status=live }}</ref>

In September 2009, Massachusetts changed its law to enable the governor to appoint a temporary replacement for the late senator Edward Kennedy until the special election in January 2010.<ref name="MA Law 54-140">{{Cite web |last=DeLeo |first=Robert A. |date=September 17, 2009 |title=Temporary Appointment of US Senator |url=http://www.mass.gov/legis/laws/mgl/54-140.htm |url-status=live |archive-url=https://web.archive.org/web/20190829050913/https://malegislature.gov/Laws/GeneralLaws/PartI/TitleVIII/Chapter54/Section140 |archive-date=August 29, 2019 |access-date=September 28, 2009 |publisher=Massachusetts Great and General Court}}</ref><ref name="Temporary Appointment Not a Candidate">{{Cite web |last=DeLeo |first=Robert A. |date=September 17, 2009 |title=Temporary Appointment of US Senator Shall not be a candidate in special election |url=https://malegislature.gov/Document/Download?entityTypeName=Journal&generalCourtNumber=186&branchName=2&entityNumber=09-22-09 |url-status=live |archive-url=https://web.archive.org/web/20210108073223/https://malegislature.gov/Document/Download?entityTypeName=Journal&generalCourtNumber=186&branchName=2&entityNumber=09-22-09 |archive-date=January 8, 2021 |access-date=July 19, 2015 |publisher=[[Massachusetts General Court]]}}</ref>

In 2004, Alaska enacted legislation and a separate ballot referendum that took effect on the same day, but that conflicted with each other. The effect of the ballot-approved law is to withhold from the governor authority to appoint a senator.<ref name="Alaska appointments">{{Cite web |date=October 28, 2009 |title=Stevens could keep seat in Senate |url=http://www.adn.com/politics/story/569836.html |url-status=dead |archive-url=https://web.archive.org/web/20090528015846/http://www.adn.com/politics/story/569836.html |archive-date=May 28, 2009 |website=Anchorage Daily News}}</ref> Because the 17th Amendment vests the power to grant that authority to the legislature&nbsp;– not the people or the state generally&nbsp;– it is unclear whether the ballot measure supplants the legislature's statute granting that authority.<ref name="Alaska appointments" /> As a result, it is uncertain whether an Alaska governor may appoint an interim senator to serve until a special election is held to fill the vacancy.

In May 2021, Oklahoma permitted its governor again to appoint a successor who is of the same party as the previous senator for at least the preceding five years when the vacancy arises in an even-numbered year, only after the appointee has taken an oath not to run in either a regular or special Senate election.<ref name=OCPA/>