An analysis of reapportionment in Idaho from James Bond’s Monkey House:
Reapportionment is a nasty, partisan business. In Idaho, a commission appointed by officials from both major parties is assigned the job of drawing new districts. Each political party wants lines drawn to give them the best chance of winning seats. There are also regional biases, with commissioners trying to draw lines that give their area of the state the maximum number of districts possible. Last time, in 2000, the southeastern part of the state lost legislative seats. There were numerous lawsuits and a lot of hurt feelings that arose from that process.
As the Treasure Valley grows, the trend seems to be in favor of Democrats. The 2010 Census could bode well for the Democrats.