Venezuela's President Nicolás Maduro speaks at a campaign rally for pro-government parliamentary candidates on Thursday. (Carlos Garcia Rawlins/Reuters)

A CRUCIAL election on Sunday may determine whether Venezuela can find a democratic path out of one of the worst crises of governance Latin America has seen in modern times. The country’s collapsing economy, soaring crime and violently polarized politics probably can be peacefully repaired only if its populist government finally agrees to negotiate with an empowered centrist opposition. In theory, there is a chance of that: Polls show the opposition leading the government by a minimum of 19 and a maximum of 30 points for the election of the new National Assembly. If the votes are counted fairly, the Democratic Unity Roundtable should win a comfortable majority of seats, giving it the ability to counter the government of President Nicolás Maduro.

What’s worrying is that Mr. Maduro is vociferously proclaiming an intention to violently resist this result. “If on Dec. 6 the right wins, prepare yourselves for a country in chaos, for violence,” he said a week before the vote. “If this happens, military comrades, you will see me in the street with you. I will never back down.” That was just one of more than a dozen similar threats issued by Mr. Maduro, who is not on the ballot.

A refusal to accept defeat would seem irrational even from the government’s point of view. Mr. Maduro, who inherited the mess created by the late Hugo Chávez and then greatly worsened it, desperately needs a political bailout. Venezuelans are furious about endemic shortages, triple-digit inflation and a poverty rate that exceeds that of 1999, when the Chavista movement first came to power. Negotiations with the opposition could provide cover to take desperately needed stabilization measures, such as the correction of a haywire currency that is worth 130 times more at the official rate than it is on the black market, and an increase in the pennies-per-gallon price of gasoline.

That Mr. Maduro instead threatens violence probably is a reflection not of his claimed commitment to “revolution” but of the regime’s deep-seated criminality. Two of the president’s nephews are being held in New York on drug-trafficking charges, and U.S. authorities are reportedly investigating numerous other senior figures, including the current president of the National Assembly, Diosdado Cabello, who is considered the regime’s second most powerful official. Opposition control of the congress would allow it to carry out investigations of corruption, and a supermajority would open the way to replacing prosecutors and judges who follow the government’s orders.

An honest vote count and peaceful outcome likely will depend on how much pressure Mr. Maduro feels from Venezuela’s neighbors and other Western democracies. Encouragingly, some are speaking up: Last week the prime ministers of Britain and Spain, together with four other present and former statesmen, released a letter saying that Mr. Maduro must ensure free elections and respect the result “if Venezuelans are to live together peacefully.” President Obama has so far been silent. But the United States should be prepared to act quickly, by pursuing multilateral censure and sanctions, if Mr. Maduro resorts to violence.