Throughout the nation's history, the governors of the states have filled most Senate vacancies by the appointment of interim or temporary Senators whose terms continued until a special election could be held. Between 1789 and 1913, the Constitution's original provisions empowered governors to "make temporary Appointments until the next Meeting of the [state] Legislature, which shall then fill such Vacancies." With the 1913 ratification of the Seventeenth Amendment, which provided for popular election of the Senate, the states acquired the option of filling Senate vacancies either by election or by temporary gubernatorial appointment: When vacancies happen in the representation of any State in the Senate, the executive authority of such State shall issue writs of election to fill such vacancies: Provided, That the legislature of any State may empower the executive thereof to make temporary appointments until the people fill the vacancies by election as the legislature may direct. Gubernatorial appointment to fill Senate vacancies has remained the prevailing practice from 1913 until the present day, with the executives of 45 states possessing some form of appointment authority, provided the candidate meets constitutional requirements. Of Senate appointments that have occurred since 1913, the vast majority have been filled by temporary appointments, and the practice appears to have aroused little controversy during that 96-year period. Aside from the death or resignation of individual Senators, vacancies may also occur when a newly elected administration is inaugurated. During the presidential transition following an election, incumbent Senators may resign to accept appointments to executive branch positions or to assume the office of President or Vice President. In 2008-2009, for instance, four vacancies were created following the presidential election: two in connection with the election of Senators Barack H. Obama and Joseph R. Biden as President and Vice President, and two more when Senator Hillary Rodham Clinton was nominated to be Secretary of State and Senator Kenneth L. Salazar of Colorado was nominated to be Secretary of the Interior. This report discusses the latest developments in vacancies in the Senate; identifies state provisions to appoint or elect Senators to fill vacancies; and reviews the constitutional origins of the appointments provision and its incorporation in the Seventeenth Amendment. One Senate vacancy was generated in connection with the 2016 election of Donald J. Trump as President. On January 20, 2017, the President nominated Alabama Senator Jeff Sessions for the office of Attorney General of the United States. Senator Sessions was confirmed by the Senate on February 8, 2017; he resigned from the Senate the same day and was sworn in the following day, February 9. In accordance with Alabama law, Governor Robert Bentley announced his appointment of state Attorney General Luther Strange III to fill the vacancy on February 9. Senator Strange, who was sworn in the same day, would serve until a special election. On April 18, Governor Kay Ivey, who succeeded Governor Bentley on April 10, ordered special primary and general elections to fill the Senate seat for the balance of the current term, which expires in 2021. The special primary was held August 15 and the runoff on September 26; the special general election was scheduled for December 12, 2017. The special election was contested by major party nominees Roy Moore (Republican) and Doug Jones (Democratic). Jones won the special election, the results of which were certified on December 28; he was sworn in on January 3, 2018. Senator Jones will serve for the balance of the term, which expires on January 3, 2021. On December 6, 2017, Minnesota Senator Al Franken announced his intention to resign from the Senate. In accordance with Minnesota law, Governor Mark Dayton announced on December 12 that he would appoint Lieutenant Governor Tina Smith to fill the vacancy until a special election could be held. Senator Franken resigned on January 2, 2018, and Senator Smith was sworn in the next day, January 3. She will serve until a special election, which will be held concurrently with Minnesota's regularly scheduled general election on November 6, 2018. At that time, the seat will be filled for the balance of the term, which expires on January 3, 2021. On March 5, 2018, Senator Thad Cochran announced that he would resign on April 1, due to reasons of health. On March 21, Governor Phil Bryant announced his appointment of Mississippi Agriculture Secretary Cindy Hyde-Smith to fill the vacancy until a special election. Under provisions of Mississippi law, the vacancy will then be filled for the balance of the term, which expires in January 2021. Senator Hyde-Smith, who was sworn in on April 9, 2018, brings the number of women Senators to a historical record of 23. The special election will be held concurrently with the regularly scheduled November 6 statewide general election. A regularly scheduled election for Mississippi's other Senate seat, the current term of which expires in 2019, and which is held by Senator Roger Wicker, is also scheduled for 2018. As a result, Mississippi voters will vote to elect two Senators on November 6: one to fill Senator Cochran's seat for the balance of his term, and the second for a full term for the other seat. Special elections for Mississippi Senate seats have certain distinctive characteristics: they are nonpartisan; there is no primary—all qualified candidates contest the special general election; and, a majority of votes is required to win. If no candidate wins a majority, the two who gained the most votes would contest a runoff election held three weeks later, on November 27. At present, five states require that vacancies can be filled only by a special election. The remaining 45 states provide some form of appointment by their governors to fill U.S. Senate vacancies. Five states currently provide that Senate vacancies be filled only by special elections; their governors are not empowered to fill a vacancy by appointment. Typically, these states provide for an expedited election process in order to reduce the period during which the seat is vacant: North Dakota Oklahoma Oregon Rhode Island Wisconsin As noted previously, 45 states authorize their governors to fill Senate vacancies by appointment. The most widespread practice is for governors to appoint temporary Senators who hold the seat until the next statewide general election, at which time a special election is held to fill the seat for the balance of the term. The National Conference of State Legislatures identifies two variations within this larger category: 36 states that provide for gubernatorial appointments to fill Senate vacancies, with the appointed Senator serving the balance of the term or until the next statewide general election; and 9 states that provide for gubernatorial appointments, but also require a special election on an accelerated schedule, often within a relatively short period after the vacancy occurs. In addition, within the first sub-category, six states also identified below require that the Senator appointed by the governor be a member of the same political party as the prior incumbent. The 36 states listed below authorize their governors to fill Senate vacancies by appointment, with the temporary Senator serving the balance of the term or until a special election is held concurrently with the next statewide general election. General elections are scheduled with relative frequency throughout the states. They are held in every state at least once in every even-numbered year, for Representatives in Congress, Senators, if applicable, and, quadrennially, for the President and Vice President, as well as for a broad range of state officials, including governors, legislators, and other state and local elected officials. In addition, a number of states schedule statewide elections for local elected officials for odd-numbered years. In several states—Hawaii, Minnesota, New Jersey, New York, and Virginia—if a Senate vacancy occurs in close proximity to a regularly scheduled statewide primary or general election, the appointed Senator serves until the following statewide election. Six of the states listed above that authorize their governors to fill vacancies by appointment also place political party-related restrictions on that power. These provisions are intended to ensure that the appointing governors respect the results of the previous election by selecting a temporary replacement who will either be of the same political party as the prior incumbent, or who has been endorsed or "nominated" by the prior incumbent's party apparatus. Arizona requires the governor to appoint a replacement Senator from the same party as the previous incumbent. Hawaii requires the governor to select a candidate from a list of three prospective appointees submitted by the political party of the previous incumbent. Maryland requires the governor to appoint a replacement Senator "from a list of names submitted by the state central committee of the political party of the vacating office holder." North Carolina requires the governor to appoint a replacement Senator from the same party at the previous incumbent. Utah requires the governor to appoint a replacement Senator from the same party as the previous incumbent. Wyoming requires the governor to appoint a replacement Senator from the same party as the previous incumbent. Some commentators have questioned these "same party" requirements on the grounds that they attempt to add extra qualifications to Senate membership, beyond the constitutional requirements of age, citizenship, and residence. Another category of states includes nine that authorize their governors to fill Senate vacancies by appointment until a special election, but require that the special election be held in relatively close proximity to the date the vacancy occurred. If the vacancy does occur close to a regularly scheduled general election, the special election may be held concurrently, but if not, the special election may be scheduled within a few months of the vacancy. This provision is intended to reduce the length of time an appointed Senator holds office before being replaced by an elected successor. In these states, the appointed Senator generally serves only until the election results for a successor are certified. The following state requirements do not include information on nomination procedures. Alabama authorizes the governor to fill a Senate vacancy by appointment. The Code of Alabama also requires the governor to order a special election if the vacancy occurs more than four months before a general election.