Gun violence has defined Sen. Dianne Feinstein's political career. The issue is more important than ever for her now

Dianne Feinstein was settling into her office at San Francisco City Hall after a two-week vacation in the Himalayas. A former colleague passed by, but didn’t respond when she called out. She heard gun shots. And then silence.

The year was 1978, and Feinstein was president of the county board of...