Actually, 10 behind Trump is not that bad for Hillary considering most the people that kernel corn vote are older farm folks in for the state fair from republican farm districts. Farmers most always are and vote republican. The inner city are liberal democrats in higher volume. And the older farm folks are a dying breed.
On the other hand, this kernel corn vote thing was quite accurate for senate candidate Joni Ernst back in 2014.
The liberal Iowan democrats are over at the beer tent getting sauced. They'd rather drink beer than drop corn kernels into a glass gar. And Iowa did go for Obama, twice. And Obama's favorable ratings are very good. So if Obama could take Iowa, twice, I'd bet Hillary can take Iowa as well. And older Iowans really love their Bill Clinton.
State republicans are just pissed off right now at the Iowa republican governor after Gov Terry Branstad declared the state fair a GUN-FREE zone.
Nothing goes together more than heat, crowds, beer, drunks, tempers, screaming kids, an even mix of rednecks and minorities, corndogs, and those guns.
The assumption that Hillary will win the overall is pretty sound bet, and for Iowa too.