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The three classes of US Senators, each currently including 33 or 34 Senators (since Hawaii became the 50th state in 1959, and until another state is admitted), are a means used by the United States Senate for describing the schedules of Senate seats' elections, and of the expiration of the terms of office of the Senators holding the respective seats.

Senatorial classes do not identify who each state's Senior and Junior Senator is - that is determined by comparing the tenures of each state's current Senators, regardless of class.

Historical division

The U.S. Constitution specifies staggered 6-year terms for Senators, and there are special provisions for getting a new state into a situation that makes that pattern continue automatically:

• around the time of the first federal elections, in 1788, each state appointed its two Senators for, respectively,
  • Class I: a two-year and a six-year term,
  • Class II: a four-year and a six-year term,
  • Class III: a two-year and a four-year term,
• upon the expiration of a Senator's term of any length, someone starts a new six-year term as Senator (based on appointment in most states, until the Seventeenth Amendment required direct popular election of Senators);
• when a new state is admitted to the Union, its two Senators have terms that correspond to those of two different classes, among the three classes defined below;
• which two classes is determined by a scheme that keeps the three classes as close to the same size as possible, i.e., that avoids any class differing by more than one from the minimum-sized class.

This means at least one of any new state's first pair of Senators has a term of less than six years, and one term is either two or four years shorter than the other. If a 51st state is admitted to the Union, it would receive Senators in Classes I and II.

Classes

     Classes 1 and 2      Classes 1 and 3      Classes 2 and 3

Class I

Class I consists of

• the 33 current Senators whose seats have been submitted to re-election in November 2012, and whose terms end in January 2013; and
• earlier Senators with terms ending in 2007, 2001, 1995, 1989, 1983, 1977, 1971, 1965, 1959, and back to 1791; and
• Current States with a Class I Senator: Arizona, California, Connecticut, Delaware, Florida, Hawaii, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming.

Class II

Class II consists of

• the 33 current Senators whose seats are scheduled for re-election in November 2008, and whose terms end in January 2009; and
• earlier Senators with terms that ended in 2003, 1997, 1991, 1985, 1979, 1973, 1967, 1961, and back to 1793; and
• Current States with a Class II Senator: Alabama, Alaska, Arkansas, Colorado, Delaware, Georgia, Idaho, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Mississippi, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, North Carolina, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Virginia, West Virginia, and Wyoming.

Class III

Class III consists of

• the 34 current Senators whose seats are scheduled for re-election in November 2010, and whose terms end in January 2011; and
• earlier Senators with terms that ended in 2005, 1999, 1993, 1987, 1981, 1975, 1969, 1963, and back to 1795; and
• Current States with a Class III Senator: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Missouri, Nevada, New Hampshire, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Utah, Vermont, Washington, and Wisconsin.

Current Senators in each class by party

As of January 15, 2007:

External links

• US Senate class page (old)
• Current Class I, (senate.gov)
• Current Class II, (senate.gov)
• Current Class III, (senate.gov)