Democrats were saying that the move was impossible, but with momentum growing they are now suggesting that the break-up is "bad for the country." 

Why is it bad for the country if a handful of conservative counties decide to freely walk away from the state of Oregon and join with Idaho?  Leftists do not explain the assertion, but one can deduce from their behavior a number of probable conclusions.   

Common arguments Democrats in Oregon and Idaho make against the move are usually an attempt to dissuade Idaho citizens from wanting to pursue secession measures.  The core claim is that the state of Idaho would have to subsidize the new counties, with Dems suggesting that rural areas are a drain on high revenue centers like Portland.