Eastern Washington is overwhelmingly conservative, except for Spokane, but it only has one-third of the population of the state. They would be happier as a part of Idaho.
However, there is a stubborn libertarian streak in Eastern Washington. In 1998, an initiative that would have banned partial birth abortion lost in every county, except one tiny county in Eastern Washington. When pollsters asked people in Eastern Washington why they voted so strongly against it, they said they didn't want government to have the power to poke its nose into their family's most personal decisions.
Spokane County went for Romney in 2012 and voted against same-sex marriage. I agree Spokane County and all other counties that border Idaho would be much happier. I know I would.