For one, overall congressional approval numbers don’t extrapolate well. Voters elect solely their own representatives, and their ballots aren’t necessarily a referendum on the entire legislative body. Last May, when congressional approval was at 13 percent, Gallup found about 46 percent approved of the job their representative was doing. This April, the AP asked a similar question, and found that while just 16 percent approved of Congress, 39 percent said they would like to see their member reelected. Of those who are most politically engaged, that figure was 44 percent.
Also, in recent years districts have become “safer” for political parties due to redistricting, as you can see in the sliding graphic to the right.
What’s becoming apparent now is that even the historically low approval of Congress during the government shutdown—Gallup had it as low as 9 percent—can’t shake this incumbent advantage.