With Rangel, Waters, Jackson-Lee, Cleaver et al, you need only look at their districts and the mentality of the residents, to see how and why they keep getting re-elected.
They have Somalia-asized their City areas.
I blame the Voting Rights Act. Here’s some probably liberal thoughts about it, though even liberals can’t hide that the whole concept was racist to the core: http://www.nationalaffairs.com/publications/detail/redistricting-race-and-the-voting-rights-act