The Idaho Constitution allows for 30-35 legislative districts, while HJR4 fixes it to just 35. Currently, this issue is being conflated with a push for one senator per county in Idaho; these are separate issues.
The short version is HJR4 is an attempt to create a 10 legislative district Ada County and the Legislature is unaware of the mathematical consequences. By having Ada County “barely” qualifying for 10 districts, this will force a minimum of 10 counties being split. The keyword is “barely.” Idaho currently has 7 counties being split.
If the population for a 10 district Ada is not obtained, Ada becomes a feeder county. An example pairing of the “north end” of Boise and Boise County would cause grief for both Boise and Ada Counties. Watch out Canyon, Gem, Boise, Elmore, and Owyhee Counties. A minimum of 9 counties will be split.
If the 10-district mark is obtained, Idaho will not have an effective ± 5% margin in redrawing lines because of “barely” qualifying. Outside of Ada, the rest of the state will have to figure out how to absorb almost half of a legislative district; extra counties will be forced split as a result. Redistricting within Ada County will become a major hassle because a small fraction of a percent will have to be shared between 10 districts. From my own personal experience on drawing Ada County maps in the last redistricting, precincts would have to be split at the front end of the process and we would have gutted pre-existing redistricting guidelines.
Finally, there are pre-existing maps with analysis involving reducing the number of legislative districts. A split in Bonner County does not have to occur. I would also like to know who is trying to split Latah County down the middle. These were presented to a few Republican legislators over two years ago; this is long before HJR4 was written. Was this information presented to their fellow legislators and to the public?
The only Republican that was identified doing a statewide analysis for redistricting Idaho 10 years ago at their Convention