How to Get Trump Voters and Liberals to Talk: Don’t Make Anyone Sit in a Circle

SAN FRANCISCO — When four Republicans and five Democrats got together at a high-end condominium complex to talk for seven hours in San Francisco this fall it was such a curiosity that a crowd of more than a dozen gathered just to watch.

Where had they found these Trump supporters in the first place, some wondered.

Why would anyone subject themselves to a day of this, others asked.

And if the day’s experiment worked — defined loosely as everyone surviving and maybe also not yelling? — were there any lessons...