The seven judges on the Oregon supreme court and the ten judges on the court of appeals are elected statewide. (They're actually mostly appointed by the governor and then elected without opposition, but in theory they're elected statewide.) This measure would divide the state into seven supreme court districts and five court of appeals districts, with each supreme court district electing one justice and each court of appeals district electing two judges. The justices and judges would have to be residents of their district when elected or appointed and remain residents of their district during their term of office.
The proponents' main argument is superficially appealing. They point out that the 17 statewide justices and judges live in only four of Oregon's 36 counties. They then say that this means that 32 counties aren't represented on the supreme court or the court of appeals. (The four lucky counties, according to the arguments in support of Measure 40, are Multnomah, Marion, Linn, and Jefferson.)
If we're going to measure diversity by geography, let's take a look at the figures. The four represented counties are Multnomah (first in population according to the 2000 Census), Marion (fifth), Linn (eighth), and Jefferson (twenty-sixth). Washington, Clackamas, and Lane Counties, the second, third, and fourth most populous counties in Oregon, have more than 1,100,000 residents (more than 30% of the state) and no appellate judges. The 18 counties east of the Cascades have 450,000 residents put together and currently have at least one appellate judge, from Jefferson County. Washington County has 445,000 residents and no appellate judges. (All these figures are as of the 2000 census.) The fact is that there aren't enough residents east of the Cascades to make up even one supreme court district, and this measure is thus no guarantee that the supreme court would always include an ultramontane jurist.
A more interesting solution to promote geographical diversity (not that anyone's asked Isaac) would be to require the governor, when appointing a judge or justice to fill a vacancy, to appoint someone from a county in which no sitting member of that court lives. But that's not the measure on the ballot. I recommend voting no on Measure 40.