Bargaining Among Partners: Mexico's 2026 Constitutional Reforms
As Mexico approaches the 2027 midterm elections, the country's new constitutional majority is reshaping the politics of constitutional change. Examining the constitutional amendments debated in 2026, Camilo Saavedra Herrera argues that the disappearance of the opposition's veto after the 2024 elections has not removed constraints on constitutional reform so much as relocated them within the governing coalition. The result is a new constitutional politics in which the key questions are no longer whether the government can amend the Constitution, but who within the governing bloc can shape, dilute, or block those amendments.
From 1988 to September 2024, amending Mexico's 1917 Constitution required cross-party bargaining. No single force commanded the two-thirds majority that Article 135 requires in both chambers of Congress, nor could they secure ratification by a majority of the 32 state legislatures on their own. Reforms were negotiated with the opposition or abandoned. That dynamic changed after the June 2024 elections, though not only through the ballot box. The National Regeneration Movement (MORENA), the left-wing party in office founded by Andrés Manuel López Obrador, had run on joint tickets with two junior allies: the Labor Party (PT), on the nationalist left, and the Green Ecologist Party of Mexico (PVEM), green in name and pragmatically unattached in practice. Together, they won a majority of votes but fell short of a supermajority.
Seat allocation closed the gap in the Chamber of Deputies. The constitutional ceiling on overrepresentation provides that no party may hold a seat share more than eight percentage points higher than its share of the vote. The rule applies per party, and candidates elected on joint tickets are credited to the party under which they registered. The coalition partners could therefore distribute their winners so that none exceeded their own limit, while the bloc's combined overrepresentation exceeded the cap by more than double. Electoral authorities upheld that interpretation over the opposition's objections. In the Senate, where the cap did not apply, defection and co-optation supplied the missing votes. That October, a constitutional reform barring judicial review of constitutional amendments placed the arrangement beyond the courts’ reach.
The new congressional composition deprived the opposition of its veto power. But the arithmetic that removed it produced a new one, according to which losing support from an ally—particularly in the Senate, where the margin is far thinner—is enough to fall short of the two-thirds majority. The reforms that once required opposition support therefore now depend on the backing of the governing coalition’s allies. In 2026, with the new congressional composition already in place, the coalition introduced six constitutional decrees addressing the workweek, public pensions, femicide, judicial elections, electoral administration, and foreign interference in elections. These decrees sustained the high amendment rate that Francisca Pou Giménez and Andrea Pozas Loyo refer to as Mexico's constitutional hyper-reformism. Electoral reforms again proved to be the hardest to pass, as they had since 2022, though for different reasons. One reform was rejected outright, another was stripped from a decree that otherwise passed, and a third measure backed by the coalition’s allies was not adopted.
What follows accounts for each: what passed and at whose initiative, what failed and over whose objections, and what remains unresolved heading into the 2027 midterm elections.
Where the Coalition Held
Two of the three non-electoral decrees introduced this year passed with near-unanimous support in both chambers, constitutionalizing established policy lines on labor rights and gender-based violence. The first, answering a decade-old union demand in the Organisation for Economic Co-operation and Development (OECD) country with the longest average workweek, cut the maximum workweek from 48 to 40 hours without wage cuts by 2030. Delayed for months by negotiations between trade unions and business associations over the transition period, the proposal was finally published on 3 March. Opposition legislators backed it while pressing for two rest days rather than one and warning that new overtime rules would leave hours effectively unchanged. The second, published on 6 May, empowers Congress to unify femicide's criminal law definition and investigative standards across the 32 states, responding to inconsistent state rules that let killings be reclassified as ordinary homicide. Opposition legislators supported it unanimously but warned it would not reduce impunity without more funding for prosecutors.
The third decree, targeting so-called "golden pensions" that allowed former officials of state-owned enterprises to draw over USD 50,000 a month against a national average of about USD 400, was submitted to the Senate on 3 March and approved unanimously by both chambers. Support began to fracture once the retroactive reach of the reform became clear: the cap, set at roughly $3,900—half the president's salary—applies to pensions already granted as well as future ones. When the Chamber of Deputies voted on the decree’s specific provisions, the opposition split: one bloc voted against and another abstained. The decree was published on 10 April. Neither the PT nor the PVEM defected; the resistance instead came from pensioners invoking vested rights and the constitutional bar on retroactive laws, and from four individual legislators.
The Electoral Reckoning
President Claudia Sheinbaum, who succeeded López Obrador in October 2024 as MORENA's second president, inherited the party’s unfinished agenda. Her predecessor failed to reform the electoral system three times: his 2022 constitutional initiative died under an opposition moratorium, the ordinary legislation version that followed was struck down by the Supreme Court for procedural violations, and the electoral piece of his 2024 package was dropped by the coalition's own negotiators before the vote.
Sheinbaum's first attempt at electoral reform reached a floor vote, only to be defeated by her party’s own allies. The commission of executive-branch officials Sheinbaum convened in August 2025 had stalled amid PT and PVEM resistance to cuts in party financing and legislative seats. Sheinbaum eventually unveiled the text on 25 February 2026, proposing cuts to public financing for parties, redesigning proportional representation in the Chamber of Deputies and eliminating the Senate's 32 plurinominal seats. These changes would have altered every party's seat share, her allies included. Sent to Congress on 4 March, the bill was rejected on 11 March, 259 to 234, with one abstention, short of the two-thirds majority required. It was the first time the allies had broken ranks on a presidential initiative. Ricardo Monreal, MORENA's floor leader, announced from the floor that the coalition would build a narrower alternative.
That alternative arrived six days later. Sent to the Senate on 17 March, the new bill dropped financing and representation entirely, capped municipal council seats and state-legislature budgets, and extended the presidential salary cap to electoral officials. It also proposed moving Sheinbaum's own recall referendum forward to the 2027 midterm elections, which PT rejected, arguing it would let her campaign on the same ballot as the vote to remove her. The Senate approved the bill as a whole on 25 March, but a PT reserva—a motion to amend a specific provision before the final vote—struck the recall clause, leaving the referendum on its 2028 schedule. The other proposals passed in the Chamber of Deputies and were published on 23 April.
The second electoral amendment to reach the Constitution responded to pressure from outside the presidency. Throughout 2025 and into 2026, United States designations, extraditions, and visa revocations over fentanyl trafficking reached dozens of Mexican politicians. The Mexican government called this foreign interference. Congress met in an extraordinary session in late May 2026 to consider two unrelated measures: a decree by Sheinbaum to postpone judicial elections, and a proposal by Monreal to amend Article 41 of the Constitution by adding foreign interference as a ground for annulling an election and creating a vetting process for candidates’ ties to organized crime. During floor debate, Monreal narrowed the scope of his proposal to require that foreign intervention be proven rather than merely alleged. PT and some opposition legislators, usually opponents, both pushed to add organized crime intervention as a parallel ground for annulment. Both attempts failed. MORENA's coordinators argued the text already covered that conduct, and a Senate reserva to the same effect was defeated, 79 to 43. The amendment passed and was published on 2 June.
Fixing the Fix
López Obrador's 2024 judicial reform is among Mexico’s most far-reaching judicial overhauls. It made Mexico the first country to elect its entire judiciary by popular vote, removing about 7,000 sitting judges at once and creating disciplinary bodies with broad sanctioning powers. Critics warned it would weaken judicial independence by placing selection in the hands of the same political majorities the courts were meant to check. The first judicial election in 2025 bore them out. Turnout reached roughly 13 percent, and much of the vote was guided by acordeones, pre-printed slates distributed by factions within the governing coalition itself.
On 20 May, Sheinbaum sent a bill to Congress—incorporating proposals from legislators across the coalition and the opposition—to postpone the second judicial election from 2027 to June 2028. She presented it as a scheduling adjustment to avoid overlap with the midterm elections, rather than as a corrective measure. Asked whether the 2025 turnout and the acordeones signaled institutional trouble, she said no, attributing the criticism to people who had lost their footing in the old judicial system. Yet the bill addressed exactly what her government publicly denied: it shortened the term of the judges elected in the 2025 round, created a commission to standardize candidate evaluation, and cut each branch's nominees per post to two, replacing the unwieldy lists of 2025. Two further provisions had nothing to do with scheduling: they set the recall referendum for that same day in 2028—fixing the specific date that the PT reserva had left unresolved in March, when it blocked the proposal to move the vote to 2027—and restored two sections to the Supreme Court, reversing a 2024 change that had forced every matter through a single, overloaded bench. Neither measure was presented as a reversal.
On 28 May, the Chamber of Deputies passed the bill as a whole, but the vote on specific provisions exposed a fracture inside MORENA itself, distinct from the ally-driven vetoes described above. A last-minute reserva, backed by Monreal, allowed sitting magistrates from the Electoral Tribunal to run again in 2028. Twenty-two MORENA legislators abstained in protest, one of them Alfonso Ramírez Cuéllar, a former national party president, who called the provision a "national embarrassment." The reserva passed the Chamber regardless, and the decree cleared the Senate and was published on 2 June, the same day as the foreign interference clause. Opposition senators called it a patch that left the politicization of judicial selection, its lack of professionalization, and the acordeones themselves untouched. The 2024 reform had failed on its own terms, and the fix was written to avoid saying so.
What Changed, What Didn't
Several matters will likely carry into 2027 unresolved. The foreign interference clause has no implementing legislation behind it. Monreal's own bill to define the term was shelved before it reached a vote, and Mexican law bars changes to electoral rules within 90 days of an election, which means that it cannot apply to next year's midterm elections and could only take effect in 2030 if Congress returns to finish the implementing legislation. The vetting process for candidates' ties to organized crime did survive, but defining participation was left to party discretion. The judiciary elected in 2025 will serve through 2028, while questions regarding its caseload and qualifications are left unresolved. The pension cap's retroactive reach has also drawn due process objections since its first days in force.
Read against previous years, 2026 combined continuity with genuine change: two things held. Constitutional reform continued to double as a political signal as much as a legal instrument. The foreign interference clause states a position aimed outward at Washington, and its main effect for 2027 is rhetorical. Coalition partners also kept voting for their institutional interests rather than any fixed ideology, a pattern also visible before 2026. What changed is the terrain on which those interests now play out. A coalition that no longer needs opposition votes can amend the Constitution on its own calendar; this year, one reform—the foreign interference clause—responded directly to sustained United States pressure, while the rest of the docket followed the coalition's own priorities.
What the allies actually stopped, across the year's points of friction, was narrower than the friction suggested. They only blocked outright the reform that would have affected their own seats and financing. On the recall referendum, they stripped a single provision and let the rest pass. The one ground that would have reached the coalition's own conduct—annulment for intervention by organized crime—faced opposition, not from the allies but from MORENA, over objections from PT and the opposition alike. The loudest protest against the judicial reform most contested addition came from MORENA's own backbenchers, not from PT or PVEM, and changed nothing. The question 2026 has so far left unanswered is therefore whether the constraint on constitutional change now sits with the junior allies or inside MORENA itself.
About the Author
Camilo Saavedra Herrera is a researcher at the Institute for Legal Research (IIJ) of the National Autonomous University of Mexico (UNAM), where his work focuses on judicial institutions, constitutional law, and elections.
Suggested Citation
Camilo Saavedra Herrera, ‘Bargaining Among Partners: Mexico's 2026 Constitutional Reforms', ConstitutionNet, International IDEA, 3 September 2026, https://constitutionnet.org/news/voices/bargaining-among-partners-mexicos-2026-constitutional-reforms