Since the Constitution says each state gets 2 Senators, and each Senator serves 6 years, shouldn’t each state (other than the original 13, for whom the Constitution explicitly gave 2 and 4 year terms to some Senators) hold their elections for their both Senators the same year? But they don’t. How is that?
Every 2 years, 1/3 of the Senate is up for re-election. No state has both Senators up for re-election in the same year.
What would be the purpose of electing both Senators in the same year? The whole point of the 6 year Senate term is that the Senate never experiences high turnover.
When new states are admitted to the Union, its two Senators are assigned to the existing classes in such a way as to keep the classes as equally balanced as possible, so one will serve for six years, and the other an abbreviated term of four or two years.
The idea is that only a third of the Senate is elected every two years. This reduces the effect of political wind and whim on the members. I suppose there is some rule that any new senators are assigned to a class by some means or another.
Of course I need to get on my now-traditional rant against the direct election of senators. But you have heard all that before.
There’s your answer. The Constitution gave these limited terms so that two years after adoption, a third of the Senate would be up for re-election (the original two-year terms), and then two years after that another third (the original four-year terms) and then two years later another third (the original six-year terms) and then two years after than, the first third again (that being six years after the re-election of this class), etc., etc. And as noted upthread, incoming states are assigned to classes such that there’s always about a third up for election each time.
The idea is to keep continuity in the Senate – not only with longer terms, but with only part of the membership up for election so the majority of senators in each Congress have been senators a while. Whereas with the House, in a spectacular landslide year, you could have a huge proportion of brand-new, wet-behind the ears representatives.
It’s a trade off between experience and deliberation vs. responsiveness to changes in the electoral mood and energy. The founding generation decided to split the difference by making one Chamber one way and the other, the other.
–Cliffy
How is that constitutional? Every Senator is supposed to serve for six years. It doesn’t say that one of a new state’s first Senators will serve a shorter term.
We enacted this ritual for the last time on August 24, 1959, when Hiram Fong and Oren Long were sworn in as the Senators from newly admitted Hawaii.
At that time there were 98 Senators–32 in Class I, 33 in Class II, and 33 in Class III. One of Hawaii’s newcomers had to be assigned to Class I–the most desirable class at that time, at its seat wasn’t up until 1964. The other would be assigned to the longer-serving of the other classes, Class III (up in 1962).
Hiram Fong won a coin flip and drew Class I. Oren Long drew Class III.
Should we ever admit a 51st state, its Senators will be assigned to Classes I and II, regardless of the date of admission.
We can’t have terms expiring in mid-Congress. Senators elected to fill vacancies only fill out the previous term, then must run for re-election. Taking a seat from a new state is considered equivalent to filling a vacancy.
You’re right, this is not explicit in the text of the Constitution, but it’s implicit in the original division into three classes.
That makes sense. Say the new Senators are filling a vacancy, instead of starting new terms, and then their terms could end before the Constitutionally mandated six years.
Ah, I agree completely. [Please mentally insert my own rant on the same topic here.]
To counter, imagine my rant on why direct election of senators, as part of the adoption of other progressive positions, saved the country. 
And mine on how we should be directly electing the president, too.
–Cliffy
Sure. In this year’s elections, in addition to the 33 Senate seats up for election in the regular course of business, there are second Senate elections in two states, each of which happens to be for the four year remander of the term left by a Senator vacating the office. In Mississippi, in addition to the race for a six year term in which Thad Cochran is running for re-election, there is a race for a four year term in the seat vacated by the resignation of Trent Lott. Similarly, in Wyoming, in addition to the race for a six year term in which Mike Enzi is running for re-election, there is a race for a four year term in the seat vacated by the 2007 death of Craig Thomas.
Note the difference in practice when a state holds a special election concurrent with a regular election, as opposed to when a state is newly admitted. In the former case, the regular election and the special election are identified in advance, and candidates seek either the short term or the full term. In the latter case, the terms aren’t identified in advance, and the winners don’t know until they arrive in Washington whether they won the short term or the long term.
Was that the case even before the 17th Amendment? Did the new state’s legislature send two Senators and the Senate had the final decision as to which one of the two available classes each would go to? Or could the state identify who should get the longer term and who the shorter?
Same deal–the legislature would elect two men, and when they took their seats they’d flip a coin or draw straws or whatever to figure out who got what.