The Mexican president's determination to carry out a contentious electoral overhaul has helped unite a fractured opposition ahead of the last major elections before the country chooses a new leader in 2024.
On Nov. 13, tens of thousands of Mexicans took to the streets to protest President Andres Manuel Lopez Obrador's plan to slash funding for the National Electoral Institute (INE) --which oversees elections in Mexico -- and reorganize the body in a way that could give him more control over it.
The protest was supported by the Institutional Revolutionary Party (PRI), helping to galvanize opposition to the overhaul which civil society groups fret risks undermining democracy under Lopez Obrador.
Opinion polls since the demonstration, the biggest against Lopez Obrador's policies since he took office four years ago, showed backing for the opposition creeping up against the ruling leftist National Regeneration Movement (MORENA).
"MORENA must learn to listen, and these are times in which we cannot be arrogant, not listen and not see what's happening in the country," said Ricardo Monreal, MORENA's Senate leader, and a presidential contender for 2024.
Resistance to the electoral reform, one of the president’s top legislative priorities, has shown the limits to his power and underlined why MORENA faces a battle to keep control of Congress in 2024 even if it is hotly favored to retain the presidency.
Before the protest, some opposition politicians had questioned the PRI's willingness to vote down the INE overhaul, threatening to drive a wedge between MORENA's adversaries.
But the demonstration revived hopes that the once dominant PRI can defend two of its remaining bastions in elections in the State of Mexico and the northern state of Coahuila next June.
Surrounding much of Mexico City, the State of Mexico is he country's most populous region and a bellwether for voter sentiment going into the presidential election race. The PRI have never lost a gubernatorial contest there or in Coahuila.
A voter survey published this week by polling firm Buendia & Marquez for newspaper El Universal showed the PRI, the center-right National Action Party (PAN) and two other opposition parties collectively eating into MORENA's still-commanding lead.
MORENA has more than twice the support of its nearest rivals, but the poll suggested that if the center-left Citizens Movement (MC) party joined forces with the rest of the opposition, elections could become significantly closer.
MC has so far shied away from working with the other opposition groups, trying to position itself as independent of MORENA and the more established opposition parties, which Lopez Obrador has pilloried as corrupt.
Some members of MC told Reuters the group could end up working with the opposition in 2023, although the party leadership has yet to endorse such a move.
Without opposition support, Lopez Obrador cannot pass his planned electoral overhaul, a constitutional reform which requires a two-thirds majority in Congress.
Debates began last week in congressional committees over the bill that also envisages reducing financing for political parties and limiting advertising time.
The president says the legislation will democratize the INE by having its commissioners elected by the public rather than by a two-thirds majority in the lower house.
However, under the reform the task of nominating candidates falls to a combination of the judiciary, Congress and the executive. Critics view that as a presidential power grab, something Lopez Obrador denies.
If the bill founders, Lopez Obrador has mooted lesser changes that only require a simple majority. But MORENA's Monreal has questioned the validity of that plan.
Lopez Obrador may have a last chance to reshape the INE when four of its 11 commissioners step down next April.
Irrespective of whether the INE controversy animates voters, analysts say it is far from clear that the opposition have found candidates that capture the public's imagination.
"Winning in Coahuila and the State of Mexico is more feasible than the presidential election," said Antonio Ocaranza, a one-time spokesperson for former President Ernesto Zedillo.
"It's one thing to agree to defend the INE and another to agree on a competitive candidate."
(Reporting by Diego Ore, Editing by Dave Graham and Alistair Bell)