Venezuelan Opposition Leader Steps Up Pressure, but Maduro Holds On

It was the boldest move yet by Juan Guaidó, Venezuela’s opposition leader: at sunrise, he stood flanked by soldiers at an air force base in the heart of the capital, saying rebellion was at hand.

Mutinous security forces supporting him had released the country’s most famed political prisoner. National guardsmen stood at Mr. Guaidó’s side as others joined marches to support the protesters that they had spent years repressing.

In the streets, anti-government demonstrators clashed with forces loyal to the president amid reports of live fire, rubber bullets and tear...