Tens of thousands of people have packed the Mexican capital’s main boulevard to protest President Andres Manuel Lopez Obrador’s proposal to overhaul the electoral authority, turning out in the largest demonstration against one of the president’s policies during his nearly four years in office.

Opposition parties and civil society organizations called on Mexicans to demonstrate on Sunday in the capital and other cities against proposed reforms that would remake the National Electoral Institute, one of the country’s most prized and trusted institutions.

Lopez Obrador sees the institute as beholden to the elite, but critics say his reforms would threaten its independence and make it more political. The initiative includes eliminating state-level electoral offices, cutting public financing of political parties and allowing the public to elect members of the electoral authority rather than the lower chamber of Congress.

It would also reduce the number of legislators in the lower chamber of Congress from 500 to 300 and senators from 128 to 96 by eliminating at-large lawmakers. They are not directly elected by voters but appear on party lists and get seats based on their party’s proportion of the vote.

The proposal is expected to be discussed in the coming weeks in Congress, where the president’s party, the National Regeneration Movement, and its allies hold an advantage.

Fernando Belaunzaran, one of the promoters of the protest, said 200,000 people participated in the march. Authorities did not confirm this figure.

Lopez Obrador has spent decades battling electoral authorities. He considers himself a victim of electoral fraud on multiple occasions although it was the National Electoral Institute that confirmed his landslide presidential victory in 2018.

Organizers have said the march was organised not against Lopez Obrador but to draw attention to the proposed reforms and to urge lawmakers to vote against them.

Lopez Obrador’s party does not have enough votes to pass changes to the constitution without support from the opposition.

Last week, Lopez Obrador dedicated a good part of his daily morning press conferences to dismissing the promoters of the demonstration, calling them “corrupt” and “cretins” who want to trick the people. He defended the proposal as seeking to reduce the electoral authority’s budget and avoiding “electoral fraud”.

While agreeing that some cost savings could be desirable, some analysts worry eliminating the state electoral offices would concentrate power too much at the federal level and sacrifice efficiency.