The vacancy language is left over from the old legislative-appointment system, under which governors could appoint temporary senators “until the next Meeting of the Legislature.” Those “temporary appointments” were limited in time—they could not last beyond the next legislative session, which was already set by state law. But the drafters of the Seventeenth Amendment, for whatever reason, specified “temporary appointments until the people fill the vacancies by election as the legislature may direct.”

See the difference? The special Senate election has no firm deadline, and the language could even be read to allow a “temporary appointment” to substitute completely for a special election.

The amendment’s language does not require appointments; it permits them if a state legislature chooses. At present, five states require immediate special elections, nine allow a genuinely temporary appointment followed by prompt special elections, and 36 allow the appointed senator to serve until the next general election—or even for the remainder of the departing senator’s term. Six of the appointment states, including Arizona, require the appointee to belong to the same political party as the departing senator.

Ambiguities aside, long-term appointment seems contrary to both the language and the spirit of the amendment; so does the same-party requirement. Legislatures should facilitate, not impede, popular elections—and they certainly shouldn’t be deciding which party gets the seat over a long period.

Eric W. Orts: The path to give California 12 senators, and Vermont just one

Some politicians see things otherwise. Control of a Senate seat is, to quote former Illinois Governor Rod Blagojevich, “a fucking valuable thing.” Blagojevich shared these musings on a federal wiretap in late 2008, when he had the chance to fill the seat vacated by President-elect Barack Obama. Although there’s no evidence that Blagojevich was able to cash in on the appointment, the crassness with which he tried to do so was one of the reasons he was impeached by the legislature and then sent to a federal prison.

Before then, Blagojevich had appointed Roland Burris to the seat; under Illinois law as it stood, Burris was to serve until 2011—the entire remainder of Obama’s term. But two Illinois voters sued over the appointment. Their claim was that the amendment requires “temporary appointments” and a special election. A statute that gave the entire remaining term to an appointee violated that provision because it was not “temporary,” and no special election would be held.

Their legal team was headed by Tom Geoghegan, a college classmate of mine who has devoted his career to fighting for labor unions and progressive causes. Geoghegan gave me the chance to run down some historical details on the passage of the amendment and subsequent cases brought under it. Eventually, the U.S. Court of Appeals for the Seventh Circuit agreed with our theory. It ordered Illinois to hold a special election.