In all my reading of American history, I can find only one constant that divides the two parties -- protectionism. We've always got a party on each side of that issue. All the other issues flutter around, and attach themselves to one party or the other.
Of course, the no tariff (or no-tariff) party usually has a degree of intellectual consistency, favoring related free-enterprise notions like less regulation, lower taxes, etc. And those issues tend to be popular in rural areas, where there's a lot of social conservatism, hence the accretion of such ideas into the free-trade party.
But trying to put all the issues of a party together into one coherent package is hopeless.