I'm with Cruz. Ethanol has done little here to prop up corn prices, and IMO distorts the market with the mandate.
There are other and better ways to deal with ag products than the existing ethanol model.
Mom grew up on an IA farm. When it came time none of the kids or us grandkids was interested in taking it over. I got curious about just how many people in IA are actually associated with ag. According to the BLS, total employment 1,632,300, non-farm employment 1,586,600. That leaves about 46,000 people on the farm. Of course, there are ancillary industries like fertilizer and machinery which are going to add a lot more jobs, but it sure seems to me like most IA voters are not involved with growing corn. Many probably still vote thinking that corn is critical to IA, but is it? If (note the "if") most farms are run by corporations not based in IA, what good, aside maybe some taxes, does ag really do for the state (and hence, why would IA voters support ethanol)?
BTW, I did some research a while back on how ethanol impacted corn/beef prices. In the few years after serious mandates were enacted, corn prices fell 60%. I'd have to say I agree with you, that's not a very good job propping up prices.