PORTLAND, Ore. — Downtown Portland businesses appear to have begun boarding up their windows again this week, bracing for possible unrest ahead of a nationwide day of protest called “Rage Against the Regime,” organized by the activist group 50501. The protest, scheduled for Saturday, August 2, is part of a national effort involving hundreds of cities, according to organizers. The central event—a peaceful sit-in—is planned at the Capitol Building in Augusta, Maine, but solidarity actions are...