Venezuelan President Nicolas Maduro speaks on Nov. 21. (Federico Parra/Agence France-Presse/Getty Images)

WITH THE world’s attention mostly fixed elsewhere, Venezuela, a country of 26 million people with some of the world’s largest oil reserves, is spiralling through a historic crash. According to the International Monetary Fund, economic output is on course to drop 10 percent this year while inflation will exceed 190 percent. Shortages of consumer goods are endemic, and the murder rate, having more than doubled in a decade, is 18 times greater than that of the United States. Many senior military and government figures have been linked to drug trafficking; two nephews of President Nicolás Maduro are being held in New York on cocaine trafficking charges.

Foreign governments watching this implosion, and many Venezuelans, have been hoping that a Dec. 6 National Assembly election could provide the beginning of a way out. The country retains a moderate opposition movement that has united into a single ticket. With polls showing it holding a double-digit lead over the ruling party, the opposition believes it should win a legislative majority — and perhaps the supermajority needed to rewrite basic laws.

The question is not whether the election will be free and fair; it already has been established that it won’t be. A remarkable 18-page letter dispatched to the electoral authority by the secretary general of the Organization of American States (OAS), Luis Almagro, painstakingly describes why. Among other things, top opposition figures (including imprisoned leader Leopoldo López) have been banned from the ballot; districts have been so gerrymandered that 52 percent of voters, concentrated in pro-opposition areas, will elect just 39 percent of deputies; and a concocted, pro-regime party with a very similar name to the opposition coalition’s has been placed next to it on the ballot.

What’s unclear is whether Mr. Maduro will resort to outright fraud or violence to prevent an opposition victory — and whether the United States and Venezuela’s neighbors, after years of silently tolerating the destruction of its democracy, will use their leverage to prevent that. Mr. Maduro is hinting at extraordinary measures; he’s said the regime will win “however” and talked of “governing with the people” if it does not. That would not be new. In the past, opposition state governors have been stripped of their powers and budgets, while lawmakers have been legally persecuted and physically attacked. But given the public mood — the percentage of Venezuelans who assess the country’s situation positively has dropped into the single digits — such tactics could trigger mass unrest.

That’s why it was encouraging to see Mr. Almagro’s letter, a rare case of a senior Latin American leader publicly challenging Venezuela’s political abuses. Another instance came in a letter to Mr. Maduro signed by 157 legislators from the United States, Brazil, Colombia, Chile, Costa Rica and Peru, including 18 U.S. senators. Developed by Maryland’s Sen. Ben Cardin (D), the text objects to the disqualification and imprisonment of opposition leaders and calls for the admittance of international election observers. The regime already has rejected monitoring by the OAS and the European Union.

More pressure should be applied to Mr. Maduro in the next two weeks, including by the Obama administration. If the vote is disrupted, the United States and other governments should be ready to respond with censure and sanctions.