The outgoing president of Mexico, Andrés Manuel Lopez Obrador, is using his last weeks in office to lead an abolishment of the country’s democratic system, using some maneuvers that are shady enough for a film noir flick.    

The president, universally known as AMLO, removed the final hurdle to a big component of his overhaul of Mexico’s political system on Tuesday night, when a proposed constitutional amendment to reform the judiciary, according to which all judges in the country would be approved by popular vote, passed the Senate by a tally of 86 to 14.

The plan, widely seen as crippling the judiciary’s independence, now needs to be ratified by two-thirds of the country’s states, which is seen as a cinch as Mr. Lopez Obrador’s party, Morena, dominates 27 of Mexico’s 32 state legislatures. 

After the proposal won the support of the lower house last week, the Mexican senate was seen as the only potential stumbling block for AMLO’s judicial takeover. To secure enough votes in the upper house, Morena used what AMLO opponents describe as unseemly tactics, including apparent backroom promises of leniency to one disgraced opposition legislator, and the arrest of a senator’s family member.

“This is a sham judicial reform, enacted by a legislature that doesn’t hesitate to use sham methods,” a former Mexican foreign minister, Jorge Castaneda, tells the Sun.

According to the proposed judiciary reform, the judges would be voted on by the public from a list prepared by politicians and sitting judges. This would likely help Mr. Lopez-Obrador to secure Morena’s hold on all government branches. It could also turn Mexico into a one-party system, as it was between  1929 and 2000.   

Ending the independence of the judiciary, though, violates the North America trade treaty known as USMCA. Most American companies would likely hesitate to do business in Mexico, fearing that any business-related disputes would be arbitrated by government-controlled judges.

“Based on my lifelong experience supporting the rule of law, I believe popular direct election of judges is a major risk to the functioning of Mexico’s democracy,” the American ambassador to Mexico, Ken Salazar, said recently, referring to the proposed judicial overhaul. 

Mr. Salazar is known at Mexico City for his friendship with AMLO, and he never interferes in local affairs. “Many people say that he is closer, perhaps, to the Mexican government than to the American government that he represents,” Mr. Castaneda told CNN recently. Rather than a personal view, though, Mr. Salazar’s statement is “the opinion of the U.S. government, which has a free trade agreement,” he said.    

The Tuesday senate vote was interrupted by protesters, as legislators on both sides clashed on the floor. It is “evident” that the government offered a senator an “impunity pact” to secure his vote, the head of the right-of-center National Action Party, or PAN, Marko Cortés, said, according to the Associated Press.

He referred to one PAN senator, Miguel Ángel Yunes Márquez, who has been in the courts on fraud charges relating to his former stint as governor of the state of Veracruz. Facing suspension from the senate, Mr. Yunes Marquez  cited health issues to vacate his seat — and transfer it to his father, Miguel Ángel Yunes Linares.

The elder Mr. Yunes then voted for the reform, and against the PAN. Morena thus got the extra vote it needed for a two-thirds senate majority, and the constitutional amendment passed. Another opposition party member, Daniel Barreda, was forced to miss the vote after his father was arrested on dubious charges at Campeche, a Morena-controlled city. 

When Mr. Lopez Obrador’s hand-picked successor, Mexico City’s mayor, Claudia Sheinbaum, won a presidential election in June, many at the capital wondered if she could distance herself from AMLO’s authoritarian, leftist populist ideology. September’s flurry of constitutional repeals would lock Ms. Sheinbaum in, forcing her to stay the course after her swearing-in on October 1. 

Next on AMLO’s chopping block are an autonomous Mexican agency, the Federal Competition Commission; the national transparency agency, which is charged with freedom of information; and the Federal telecommunications agency. Morena also plans to put the independent Federal Election Commission under government control.

During AMLO’s final month in office he is dismantling institutions that were set up 40 years ago. Reformed bodies created political competition to the oxymoronically named Institutional Revolutionary Party, or PRI, which governed Mexico longer than the communists held power in Russia. Democratically oriented reforms made Mexico more economically prosperous, and also a better American ally. 

Mr. Lopez Obrador launched his political career as a PRI politician. After leaving and creating the Morena party, he now is returning Mexico to the days when one party, this time his own, would dominate. His hopes are that it will remain in power at least as long as the PRI did.