Reforms to Mexico’s electoral system have inspired some of the largest protests of the current president’s tenure.

On Sunday, tens of thousands of people filled the main plaza — or Zocalo —  in Mexico City, with thousands more attending protests across the country —  including the Sonoran capital Hermosillo. They were protesting recently approved reforms that they say weaken the nation’s electoral institute and, in turn, Mexican democracy.

On Monday, Mexican President Andrés Manuel López Obrador, a key proponent of the reforms, acknowledged the sizable turnout, but said it pales in comparison to mobilizations that he has called.

He said the opposition would do well to observe turnout at another event planned for mid-March to commemorate the nationalization of Mexico’s oil resources in 1938.