The US Constitution requires that, to move those counties from Oregon to Idaho, Congress, the Oregon state government, and the Idaho state government would all

The US Constitution requires that, to move those counties from Oregon to Idaho, Congress, the Oregon state government, and the Idaho state government would all have to approve the transfer. Not only that, but they'd have to decide what is to be done about debts, state property, and any ongoing projects that the Oregon state government is currently paying for. Politically, if the move were to actually take place it would help Democrats slightly, by making remaining Oregon more solidly Democrat (though those counties are almost empty).