As a lifelong Iowa resident, I would caution against getting too excited about this.
Iowans who go to the fair are not like those who vote. Far from it. The demographics are way off. The rural-to-city folks ratio is extremely skewed, with the city dwellers vastly underrepresented.
(No one trolls the inner city with cigarettes and malt liquor to entice the folks to hop on the bus and go to the FAIR to vote for Democrats.)
LOL, true. But inner city is not going to come out like they did for Obama, and last poll I saw showed Trump getting an amazing 14% of the black vote. So we can hope !!