Here's a different question. Whether it's the published rankings (which are different from these) or whatever you think the "real" rankings are, how much does it matter if you go from 30 to 20? Or from "the abyss" to 30? Again, not arguing about which schools are at these ranks, but just how different are things for faculty and students?
Perhaps a better way to think about it would be resources the department provides, the median outcome for the median student (which is where more complete lists of entering and exiting cohorts would help), and which faculty members out of all those listed on the website actually work with students.
For instance, at two of these "C" Tier schools a few years ago, one program offered $15k a year (only 4 years guaranteed) with required TAing/RAing while another offered $27k a year for 5 years with very limited TAing/RAing. That's an enormous difference, even with adjustment for cost of living.
Another program was notorious for faculty discontent (constantly going on the market and several leaving each year), which boiled over into very few of the "name-brand" faculty working with grad students and negatively affected placement, even though the financial package and USNews ranking were quite good. Even smaller things like how much travel/conference funding is guaranteed can add up; it's much easier to attend conferences with $1000 in institutional funds rather than a pitiful $250.
There's actually a decent bit of variety in the approaches to grad education and polisci more generally (the nebulous but real "fit" concept) between programs that's hard to tell from the outside and especially during the dog-and-pony show recruitment visits, so talk with 4th/5th year grad students and especially recent grads from each place to get a more accurate picture. Faculty are often clueless about what the grad student experience is actually like and how it compares to other places.
All said, any of the programs listed in this ranking could work for the right student. I might say that it's worth going down one tier if you have a good fit/package in the tier below compared to an poor fit/bad offer in a higher tier. The "abyss" is putting it too unkindly below the current tiers since there are bright spots elsewhere (especially if you have a strong regional preference), but if you're not getting into at least a few of the ones listed here in the first place you should probably reconsider grad school.