MEXICO: The Yen to Riot

In its three-phase process of nation building—revolution, industrial development, prosperity—Mexico is well into Phase 2, and President Adolfo Lopez Mateos is determined to keep going. To do the job, he needs political stability. Instead, Lopez Mateos is now bedeviled by leftist demonstrations and violence that resulted last week in the jailing of Mexico's No. 1 artist and No. 1 Communist, David Alfaro Siqueiros.

The violence grows partly out of the fact that the memory of the Mexican revolution is so fresh and inspiring; the initials of the ruling party, P.R.I., stand for Party of Institutionalized Revolution. Although the revolution started...