Via Public Policy Polling:
When we did our Michigan poll last weekend obviously we didn't know Carl Levin was going to announce his retirement this week, so we didn't test any other potential Democratic candidates. Our poll numbers on him do give a prism into the comparative strength of some of the possible Republican candidates though. The one who came the closest to Levin was Candice Miller, although she still trailed him 46/35. She has good statewide favorability numbers with 33% of voters rating her favorably to 25% with an unfavorable opinion.
No one else came within 15 points of Levin. Justin Amash has a 9/20 favorability rating and trailed Levin 49/34. Mike Rogers has a 16/19 favorability rating and trailed Levin 49/33. Bill Schuette has a 20/25 favorability rating and trailed Levin 51/32. And Roger Kahn had a 5/15 favorability rating and trailed Levin 50/30.