Are politicians attempting to destroy tenure? Apparently, Iowa's politicians intend to enrich the tenure experience by annual gladiatorial games at state schools, regardless of tenure:


those being evaluated below some threshold shall be terminated, and
after (1), the 5 remaining lowest scoring professors will be put to a public student vote, and the one with the least student support shall be terminated.


The source looks legit - blog of the AAUP. I'm not sure if this is enacted, or proposed (I think proposed). I'm also not entirely sure how to link this to an answerable question fit for Academia.SE, but maybe: 


Is this a joke I didn't get, or is it true?
Is it part of a broader wave?  
Does this contradict any case law, or is being fought already somehow; or will professors just have to live with it? 


If this is true, and stands in Iowa, to be worried for the US at large one just has to look at how quality of life legislation spread like a wild fire once enacted in one place.
Proposals to "reform" or end tenure are not new—they have been going around for several decades at least (as I remember such stories when I was an undergraduate in the 1990's).

This is not yet enacted legislation—it is merely a proposal that, as far as I can tell, probably has not even had any hearings yet. As such, I would suspect that such a bill would be shot down in committee, as the proposed methods would probably violate at least some sort of labor laws, as the faculty would in effect be judged by students with whom they have never interacted. Such "popularity contests" would pretty much dry up any opportunities for faculty recruitment. (Who would want to work at such a school?)