Depending on the state, not enough to matter. Farmers are not a major voting block in most of the US anymore. Farmers are a bit over 1% of the US population. I'm trying to find better sources than listicle type things, but the best I can find is that in the states with the highest percentage of farmers, it's still only 5-6% of their state population.
That can be enough to swing things, but it's not enough to be the deciding block that many think they are. A century ago things were much different.