
Devin H. answered 05/03/19
Graduate of Catholic School with 2 Years of Catechism Experience
https://morningconsult.com/2019/01/10/americas-most-and-least-popular-senators-q4-2018/
The above link is to a poll taken every quarter on the approval ratings of people's individual senators. Though as your citation states, approval ratings of Congress as a whole clock in as low as 20% (and in many cases even lower), it is informative to consider that this does not reflect, in many cases, people's views of their own representation. Notably, 87 senators polled here had a higher favorability rating than unfavorability, and 23 of them had at least 50% approval, even counting the "don't knows" more ambivalent about their senators' job performance. As to the other 13... re-election awaits.
From an individual perspective, this makes sense. It's much easier to be disgruntled at the 434 representatives and 98 senators one can't replace than at the representative and 2 senators one actually did elect.