DCCC updated their list of the weakest Democratic incumbents (excluding Dem v Dem primaries due to redistricting).
http://dccc.org/blog/entry/dccc_chairman_steve_israel_announces_new_frontline_members/Interestingly, Heath Shuler, rated by Cook and Rothenberg as endangered is not on the list, further supporting the rumor he will retire.
The 18 most endangered Democratic incumbents are:
Ben Chandler (KY-06)
Betty Sutton (OH-16)
Bill Owens (NY-23)
Dave Loebsack (IA-02)
Gabby Giffords (AZ-08)
Gerry Connolly (VA-11)
Jerry McNerney (CA-11)
Jim Matheson (UT-04)
John Barrow (GA-12)
John Garamendi (CA-03)
Kathy Hochul (NY-26)
Kurt Schrader (OR-05)
Larry Kissell (NC-08)
Leonard Boswell (IA-03)
Lois Capps (CA-24)
Mike McIntyre (NC-07)
Tim Bishop (NY-01)
Tim Walz (MN-01)