Article 1, Section 3, Clause 2 of the US Constitution deals with the staggered terms of office for the members of the US Senate. It also deals with filling vacancies when they occur in the Senate.
“Immediately after they shall be assembled in Consequence of the first Election, they shall be divided as equally as may be into three Classes. The seats of the Senators of the first Class shall be vacated at the Expiration of the second Year, of the second class at the Expiration of the fourth Year, and of the third Class at the Expiration of the sixth Year, so that one third may be chosen every second Year; (and if Vacancies happen by Resignation, or otherwise, during the Recess of the Legislature of any State, the Executive thereof may make temporary Appointments until the next Meeting of the Legislature, which shall then fill such Vacancies.)” Article 1, Section 3, Clause 2
The part of the Clause above in parentheses was amended by the 17th Amendment, second paragraph:
“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 vacancies by election as the legislature may direct.”
Three Classes
The language of this section is difficult to follow. I will make an attempt at explanation so that we can sort out “Who’s On First?” (This is a reference to a skit done many years ago by Abbot and Costello).
The concept that the Founders were conveying with the three “classes” was that every two years, one-third of the Senate would be up for re-election (reappointment, initially). There would always be 2/3’s of the body that were familiar with the issues and procedures of the day. This allowed for the Senate to have more continuity and experience in their approach to current legislation.
In 1789, when the first Senate convened, the Senators were divided into three classes. The division was done by lottery. The term of the First Class of Senators would expire in 2 years, the Second Class in 4 years, and the Third Class in 6 years. This allowed for the terms to be staggered so that every 2 years, one-third of the Senate is re-elected (reappointed initially). Since that initial adjustment, each term is 6 years. This system has continued with the addition of new states.
A list of the Senators with the Class information can be viewed here: http://en.wikipedia.org/wiki/List_of_current_United_States_Senators
Please note that Class 1 will be reelected in 2018, Class 2 in 2014, and Class 3 in 2016.
Another reference concerning the Classes: http://en.wikipedia.org/wiki/Classes_of_United_States_Senators
In Pennsylvania, Senator Pat Toomey will be up for reelection in 2016 and Senator Bob Casey in 2018 (Casey was reelected in 2012).
Filling Vacancies
In the original Constitution (before the 17th Amendment), vacancies in the Senate were filled by an appointment by the State legislature. If the legislature was not in session, the Governor could appoint a temporary replacement until the State legislature could appoint someone to fill the seat.
With the 17th Amendment, provision is made for the Governor (executive authority) to make the temporary appointment until an election is held, if the State legislature had previously allowed for the Governor to make the appointment. If the State legislature has not made provision for Governor to make the temporary appointment, then the seat would remain vacant until a special election is held to fill the seat. Under the original Constitution, the Governor was allowed unconditionally to make the appointment.
Under Clause 2 of Article 1, Section 3 we the people give the opportunity to elect one-third of the Senate every two years.
The benefit to us is that we have continuity and experience in the Senate, but we the people can survey the actions of the Senate every two years.
References:
Findlay, Bruce Allyn and Findlay, Esther Blair. Your Rugged Constitution. Stanford: Stanford University Press, 1950
US Constitution
Wikipedia, Article One of the United States Constitution
Reclaiming the Shining City 