Debbie Stabenow is in deep trouble in Michigan. An average legislator with good timing (elected in 2006 and reelected in the Democratic wave of 2006) she's in for the fight of her life in 2012. With plenty of Republicans who have good name recognition and such a high dissatisfaction with the President by the average Michigan voter she's highly vulnerable. Unless the Republicans nominate somebody totally unacceptable Stabenow should lose.
Claire McCaskill is in even greater danger. Scraping by in 2006 over Jim Talent she's rapidly becoming a conservative to make herself electable but this strategy is ultimately pointless. I'll say it right now-there is no way she's reelected. Missouri has turned brighly red and there's no reason to think it will be any different in 2012. Roy Blunt, an average GOP candidate, destroyed his Democratic opponent last month carrying every area of Missouri except for metro St. Louis and Kansas City. Like Michigan there are plenty of quality GOP opponents and they'll be rapidly announcing their candidacies in the next few months.