Venezuelans attend a Dec. 13 concert in Caracas celebrating the victory of the opposition in parliamentary elections this month. (Miguel Gutierrez/European Pressphoto Agency)

SINCE THE landslide victory of a Venezuelan opposition coalition in elections for the National Assembly this month, civil society leaders and foreign governments have urged President Nicolás Maduro and his ruling party to accept the results and negotiate with the victors about ways to stabilize Venezuela’s crashing economy. Sadly, they have been ignored. Mr. Maduro and the regime’s next most powerful figure, outgoing assembly president Diosdado Cabello, have instead embarked on a radical campaign to reverse or neuter the election results. The result is a growing danger that a major oil-producing nation will be pushed into a potentially violent domestic conflict.

Venezuela’s problems are already profound. The economy has contracted by 10 percent this year, according to the International Monetary Fund, and the inflation rate is in triple digits. Shortages of basic consumer goods are widespread, forcing consumers to spend hours waiting in line for items such as cooking oil and toilet paper. The murder rate is believed to be the second highest in the world. And the opposition’s victory came in spite of the fact that scores of its members have been imprisoned, including Leopoldo López, who is one of its top leaders.

The opposition Democratic Unity Roundtable (MUD) expressed its willingness to negotiate with the government after winning 112 of 156 seats in the Dec. 6 elections. Though the two-thirds majority it holds in the National Assembly gives it the power to force a recall referendum on Mr. Maduro or even rewrite the constitution, MUD’s leaders recognized that the 74 percent of Venezuelan voters who turned out desperately want economic remedies.

The regime’s response has been inflammatory rhetoric and illegal manuvers. Mr. Cabello convened an unelected “communal Congress” composed of hard-line government supporters and allowed it to take over the National Assembly’s building. On Wednesday, the government’s lame-duck parliamentary majority rushed to appoint 13 new members to the Supreme Tribunal of Justice, the nation’s highest court. The 32-member court is already packed with government partisans, and the new appointments are meant to ensure that no other justices are seated for years to come. The nominees included stalwarts of the ruling party, in violation of constitutional norms.

Of still greater concern are suggestions from ruling-party figures that they could seek the reversal — by the same court they just restaffed — of the election of 22 opposition deputies. There are no plausible grounds for the claims of irregularities in the balloting. But the cancellation of opposition victories, which would deprive the MUD of the supermajority that gives it crucial leverage, could provoke a resumption of the mass street demonstrations that last year led to the deaths of more than 40 people.

Pressure from outside parties, including the United States, could head off such an outcome. There are indications that some in the regime, including senior military leaders, oppose the radical strategy that Mr. Maduro and Mr. Cabello have embraced. Now is the time to make clear that the regime and its leaders, including those in the security forces, will be held responsible for a rupture of democratic order and for any use of force against the opposition.