Shootings Spur Debate on Extremism and Guns, With Trump on Defense

The politics of American gun violence follow a predictable pattern in most cases: outraged calls for action from the left, somber gestures of sympathy from the right, a subdued presidential statement delivered from a prepared text — and then, in a matter of days or even hours, a national turning of the page to other matters.

But after a white supremacist gunman massacred 22 people in El Paso, the political world hurtled on Monday toward a more expansive, and potentially more turbulent, c...