Growing tensions within President Andres Manuel Lopez Obrador’s party risk derailing his plan to pick a candidate to succeed him in Mexico’s 2024 election.

Leaders of the ruling Morena party met behind closed doors on Thursday to agree on details of the plan, which entails a number of national polls to determine the candidate, but representatives for half of the six presidential hopefuls voiced reservations about the pollsters chosen, according to a person familiar with the matter.

Ex-Foreign Minister Marcelo Ebrard’s representative rejected the agreement, while aides for former Interior Minister Adan Augusto Lopez and former Senate majority leader Ricardo Monreal signed it with reservations, the person said, asking not to be named discussing internal party matters. The disagreement was first reported by local media.

The pollsters were chosen through a lottery system, but Morena leaders decided not to reveal their names until after a candidate is picked on Sept. 6 to “protect them from external pressures,” according to Mario Delgado, the party’s national head.

Lopez Obrador has vowed not to interfere in the candidate’s selection, but concerns about the opacity of the system are fueling discontent among some presidential hopefuls, many of whom had to resign from high—ranking government positions to compete for the nomination. Tensions hit a high point on Wednesday when Ebrard said Morena’s leadership was favoring former Mexico City Mayor Claudia Sheinbaum, his main rival in the race for the nomination.

Opaque Process

Whoever is chosen will be in a strong position to become Mexico’s next president, tapping into Lopez Obrador’s high popularity.

The decision not to name the pollsters “will raise further questions regarding the transparency of the internal process, which has already been marred by controversy,” Alejandro Schtulmann, research director at Mexico City-based political consultancy EMPRA, wrote in a research note.

Lopez Obrador, who’s not eligible to run for reelection in June, reaffirmed his confidence in the process on Friday.

“I support the work of party leaders, I support those carrying out the process and trust them,” the president known as AMLO said at a news conference. “I will support the result of the survey.”

Read More: Mexico’s AMLO Denies Playing Favorites in Vote Lead-Up

The four external pollsters that have been selected are expected to be vetted on Friday by a party committee that will verify whether they have the necessary experience, the technical requirements and sufficient staff, Delgado said. Firms whose poling numbers were “discordant” with the outcome of the past eight state elections in 2022 and 2023 were removed from the lottery, he added.

The meeting on Thursday lasted more four hours as representatives for the six presidential hopefuls debated the methodology of the process that will select a “national coordinator” for the campaign, or the person who’s expected to become the party’s candidate next year.

--With assistance from Maya Averbuch.

(Recasts story with details of Thursday meeting, comments from AMLO and analyst.)