Protesters demanding elections and a return to democratic rule jammed the streets of Caracas and other Venezuelan cities on Wednesday. National Guard troops and government-aligned militias beat crowds back with tear gas, rubber bullets and other weapons, and at least three people were killed, according to human rights groups and news reports. President Nicolás Maduro defied international calls, including a plea from the American State Department, to allow peaceful assemblies and ordered his forces into the streets. Some demonstrators, wearing masks to protect themselves from tear gas, fought back with firebombs. Still, despite the deaths in recent protests, now numbering seven, Wednesday’s rallies attracted thousands of people, the latest in a string of demonstrations against the increasingly autocratic rule of Mr. Maduro. Labeled by organizers “the mother of all protests,” it showed that a sustained movement in the streets against Mr. Maduro may now be forming. […]