In the 1787 Constitution, senators could only be chosen by legislatures; but legislatures were often not in session. So Article I § 3 cl. 2 stated that, when a vacancy arose "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." But because the House was and is elected by the people, no appointment is ever permitted: when a House seat falls vacant, "the Executive Authority thereof shall issue Writs of Election to fill such Vacancies."
The earlier language about appointment seems to have been written into the new amendment without much discussion. (If there was any, I couldn't find it in the record.) But its logic is flawed: Senators now represent the people, and "writs of election" can be issued for Senate, as well as House, elections. The ambiguous new language allows the legislatures if they choose to empower their governors to make "temporary appointments until the people fill the vacancies by election as the legislature may direct."
A large number of states simply permit the governors to appoint a replacement until the next regular election -- or, as New Jersey does, to do so when the calendar makes it inconvenient to hold a special election sooner. Four states, including my beloved Oregon, forbid the governor to make any appointment. Instead, a Senate vacancy is treated like a House vacancy, filled only by a special election held as soon as possible.
The Senate is now as much "the people's house" as the House, and there's no reason to allow the governor to interpose his individual choice between the people and their senate seat. Nonetheless, the language permits that. But it requires something else--that the appointment be "temporary." If, as in the New Jersey case, the appointee may serve the entire unfilled term of the departed senator, that appointment is in no sense "temporary." Lautenberg's elected, "permanent" term ends in January 2015. If we give ordinary sense to words, a "temporary" appointment can't include the entire remaining term.
In 2008, Barack Obama vacated his seat with a little over two years left in his term. Using Illinois law, Blagojevich awarded that seat to Roland Burris; but, I am proud to say, Burris did not serve the entire remainder of Obama's term.
A team of lawyers (I was a consultant) brought a lawsuit against the Governor of Illinois demanding a special election. (By this time, Blago had toddled off prisonwards, and his replacement was Pat Quinn.) The Seventh Circuit, in an opinion by Judge Diane Wood, agreed: "Our analysis of the Seventeenth Amendment led to the conclusion that a state must hold an election each time that a vacancy occurs in its Senate delegation, so that the people of the state can elect a replacement senator. To ensure that such an election takes place, the executive officer of the state is required by the Constitution to issue a writ of election." By that time, the case had dragged on so long that there was very little time remaining in the term. Nonetheless, Election Day 2010 saw two elections on the Illinois ballot -- one for the upcoming six-year term and one for the 62 days remaining on Obama's term. It may seem silly, but it made Senator Mark Kirk senior to the other members of the Class of 2010.
Of course, New Jersey is in the Third Circuit, not the Seventh; and in fact, an earlier New York case about the timing of the election to replace Sen. Robert F. Kennedy (D-NY) had held the opposite. (For complicated reasons, its effect as precedent is questionable.)
But Christie and his lawyers are in a unique position: They must choose between two directly conflicting statutes. One would follow the Seventh Circuit approach. The other would permit the appointee to serve Lautenberg's entire term.
Constitutional stewardship would be best served by choosing the statute that accords with the wording of the Seventeenth Amendment.
But now that we've had a good laugh over the idea of stewardship, let's see which statute Christie believes will best advance his own and his party's fortunes. Political advantage, to most politicians, is the only point of a senate, after all. They tend to phrase the thought more elegantly than Blago did, but the meaning is the same.