Thousands of people have taken to the streets of Mexico City to demand the president's resignation.
Protesters gathered as anger mounted over President Enrique Pena Nieto's handling of drug violence, corruption - and his meeting with Donald Trump.
Cries of "resign now" rang out as they marched to the Zocalo square on the eve of Mexico's independence day holiday.
Mr Pena Nieto's approval rating has dropped to 23%, according to a recent survey by Reforma newspaper.
Mexicans traditionally gather in the Zocalo square the night before independence day celebrations to see the president come out to the balcony.
Once there, the leader is supposed to replicate the "grito", or shout of independence, made in 1810.
But on Thursday, the mood was not one of celebration.
Instead, demonstrators waved blackened Mexican flags and held a sign "Pena Nieto INEPT, RESIGN for the good of Mexico!", and were blocked from entering the square by riot police.
Among the crowd were the parents of 43 students who went missing in September 2014.
"We don't have a reason to shout 'viva Mexico' ... There are thousands of injustices," Cristina Bautista, mother of one of the missing trainee teachers, told AFP.
The missing students are considered by some observers as one of the reasons why Mr Pena Nieto's approval rating has dropped so low.
But Mr Trump's visit on August 31 shook his administration, with finance minster Luis Videgaray - who was reported to have spearheaded the meeting - resigning in its wake.
Trump has made repeated calls for a wall to be built along the US-Mexico border to stop the flow of migrants and refugees.
The Republican presidential hopeful has also accused the country of sending rapists, drugs and crime to the US, angering Mexicans and campaigners who labelled the comments "absurd".