Idaho
Outlook: Safe Republican
Fairly popular Republican Governor Dick Kempthorne is out, leaving unfortunately-named Congressman Butch Otter as his likely successor. Otter, elected with 70% in his northern Idaho district in 2004, is probably more threatened by jokes about his full name ("Butch" is a nickname, by the way - his real name is Clement Leroy Otter) than anyone the Democrats can put out. Although Otter is on the record as being against the PATRIOT Act, he's unlikely to face a significant primary challenge.
Though I agree with you that Otter is the front-runner, Lt. Governor Jim "Prince of Darkness" Risch is also running. He spent thousands of dollars in the 2002 primary for that position, ousting the incumbent Republican. Everyone knows he has his eyes on the Governorship.
Also, the Democrats are running 02 nominee Jerry Brady. He came within 10 or so of Kempthorne then, but that was a good year for Idaho Democrats and I don't expect him to do any better.