The democrats fought bitterly at times over banking policies

I believe the answer is: Slavery issues,  tariff rates, and banking policies.

The democrats mostly consist of 2 groups. The center leaning democrats and the extreme left democrats.

The center leaning democrats stands for personal liberty and do not want the government from taking much involvement in people's life or the free market while the far left is quite the opposite and this influence them in slavery issues , tariff rates, and banking policies.  The other part of the party has a quite the opposite view.

b). (sounds as the best answer)

. political or economical policy that isolates a country from participating in international relationships. it has been suggested that the united states participates in isolationism because of its lack of involvement in particular wars or alliances.