The incumbency factor in US politics means that the seats most likely to be won by the other party are the so called "Open Seats". This is bad news for the Republicans, since they have a much larger number of retirees. Using The Cook Political Report the following are the Open Seats in the House of Representatives most at risk of being lost by the Republicans
Polling suggests good chance of a turnover -
Arizona 01
Illinois 11
New York 13
New York 25
Virginia 11
Open Republican seats currently too close to call -
Alabama 02
Louisiana 04
Minnesota 03
New Jersey 03
New Jersey 07
New Mexico 01
Ohio 15
Ohio 16