It's counterintuitive but the most divisive arrangement is when the same party controls both Congress and the presidency a situation encountered in eight of the past 10 years. With government unified under a single party the minority has the least possible incentive to cooperate with the majority.
My dad spent his whole life getting into fights for telling what he believed to be the truth. Basically it comes from my dad-and he's screaming right-wing so there you are.