On July 16, more than seven million Venezuelans voted in a plebiscite that emphatically rejected President Nicolás Maduro’s plans to convene a Constituent Assembly to rewrite the Constitution. It was a remarkable showing for a D.I.Y. electoral event and included robust, if nervous, turnout in the working-class districts that were once strongholds for Mr. Maduro’s predecessor, Hugo Chávez.

Since the plebiscite, Venezuela’s opposition has taken steps toward establishing a parallel government. This might remain a symbolic initiative. But if the opposition continues down this road, itwill soon be looking for international recognition and funding, and will at least implicitly be asserting the parallel government’s claim to the legitimate monopoly on the use of force. After that itwill seek what every government wants: weapons to defend itself. If it succeeds, Venezuela could plunge into a civil war that will make the current conflict seem like high school fisticuffs.

It is hard to blame the opposition for considering the path of parallel government. Almost four months of street protests against Mr. Maduro’s dictatorship have resulted in 100 deaths. Hopes that the Organization of American States could enforce its Democratic Charter have been repeatedly dashed. And the Maduro government, with a Leninist tenacity that sees struggle as the opportunity to consolidate its project, refuses to withdraw its plans.

The response of the Trump administration has been to suggest that it is looking to add names to the existing program of United States sanctions, and is considering broader economic sanctions. But such unilateral sanctions will almost certainly make Venezuela’s already dire situation worse.