Political compatibility is less about identical opinions than the consequences those opinions have at home. Views on children, money, religion, gender roles, firearms, community, and where to live can become household decisions.
What matters in practice
Before treating party registration as a shortcut, ask what a belief changes in practice. Two people may vote together for different reasons—or vote differently while building nearly identical lives.
The test is whether disagreement remains respectful and whether both people can make joint decisions without contempt. Chemistry can survive debate; it rarely survives humiliation.