Too much fighting in politics has come from most issues being diluted into left or right, blue or red, Democrat or Republican. These two parties have become catch all polarization for hundreds of issues, and party leaders expect members to hold all the issues if they hold one of them.
Limit party affiliation to 25% of the population on county, state, and national levels. If 25,001 people in a 100,000 person county want to join the Pickle Party, then they have to split or start a new party; Pickle Party East and Pickle Party West, for instance.
This will encourage parties to be less hard-line on polarizing issues. e.g.: even though Pickle Party East and West both support pickles, maybe East prefers dill and West prefers bread-and-butter. More divisions creates more variations, and ensures that no party becomes a cult-like and monolithic power base.