As of Now: 52 Democratic Incumbents who ran and lost; most were from very Red CDs

Here is a list of Congressional Districts in which an incumbent Democrat ran and lost AND the seat was filled by a Republican (WV 1: the incumbent Democrat lost in the primary and the primary winner lost in the general election)

I’ve listed the CD’s along with the Presidential winner in 2008, 2004, and 2000. The last number is the number of times that a Republican president won that district (data from here)

So: 26 of these losses came from districts in which 2008, 2004 and 2000 by the Republican presidential candidate.
14 of these had the Republican president win 2 out of the 3 times
6 of these had the Republican president winning once
6 had elected the Democrat every time.

Or, put another way, 40 of the 52 Democratic incumbents who lost represented “red” or “reddish” districts.
This does not include the currently undecided seats nor those in which the sitting Democrat didn’t run for reelection and the seat switched hands.

WV 1 Mc, B, B 3
AL 2 Mc, B, B 3
AZ 1 Mc, B, B 3
AZ 5 Mc, B, B 3
CA 20 O, K, G 0
CO 3 Mc, B, B 3
CO 4 Mc, B, B 3
FL 2 Mc, B, B 3
FL 8 O, B, B 1
FL 22 O, K, G 0
FL 24 Mc, B, B 3
GA 8 Mc, B, B 3
ID 1 Mc, B, B 3
IL 11 O, B, B 2
IL 14 O, B, B 2
IL 17 O, K, G 0
IN 9 Mc, B, B 3
MD 1 Mc, B, B 3
MI 7 O, B, B 1
MI 8 O, B, B 1
MS 1 Mc, B, B 3
MS 4 Mc, B, B 3
MO 4 Mc, B, B 3
MN 8 O, K, G 0
NV 3 O, B, G 2
NH 1 O, B, B 1
NJ 3 O, B, G 2
NM 2 Mc, B, B 3
NY 13 Mc, B, G 2
NY 19 O, B, B 2
NY 20 O, B, B 2
NY 24 O, B, B 2
NC 2 O, B, B 2
ND Mc, B, B 3
OH 1 O, B, B 2
OH 6 Mc, B, B 3
OH 15 O, Tie, B 1-1-1
OH 16 Mc, B, B 3
OH 18 Mc, B, B 3
PA 3 Tie, B, B 2
PA 8 O, K, G 0
PA 10 Mc, B, B 3
PA 11 O, K, G 0
SC 5 Mc, B, B 3
SD Mc, B, B 3
TN 4 Mc, B, B 3
TX 17 Mc, B, B 3
TX 23 O, B, B 2
TX 27 O, B, Tie 1-1-1
VA 2 O, B, B 2
VA 5 Mc, B, B 3
WI 8 O, B, B 2