What did Otter do, exactly? Could a Democrat win in Idaho?
I guess, Walt Minnick (DINO) pulled out a plurality in his House district in 2008, but it seems like a bar Democrats are unable to attain.
I was actually just in Idaho last weekend visiting friends, and because I have no self control I asked them what they all thought of Otter. Everyone's perception of him is pretty meh (they all know him because of his name, well to be fair, he's been involved in ID politics for decades). He gets high approvals because (and this is quoting someone) "there's nothing to do as governor of Idaho."
Conclusion: he should be reelected without any significant issues.