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(THE CONVERSATION) Former Supreme Court Justices Ruth Bader Ginsburg and Antonin Scalia were on opposite sides of the political spectrum. Yet despite their obvious legal disagreements, the liberal Ginsburg once described herself and the conservative Scalia as "best buddies."

This connection across ideological lines may seem surprising today. A striking feature of the current political moment is the extent to which it has affected personal relationships, with friendships fissuring o...