A mass rally of supporters of defeated Mexican presidential candidate Andres Manuel Lopez Obrador has "elected" him head of a parallel government.
Hundreds of thousands of protesters gathered in Mexico City's main square, the Zocalo, for the show of hands.
Mr Lopez Obrador and his supporters have said his defeat by less than 1% of the vote was fraudulent.
However, the highest electoral court has backed the result, giving power to conservative candidate Felipe Calderon.
The demonstrators had flocked to the square after an earlier military parade to mark Independence Day that was overseen by outgoing President Vicente Fox.
Mr Lopez Obrador's supporters had been told to come for a National Democratic Convention.
They voted to swear him in as the "legitimate president" on 20 November, 11 days before Mr Calderon is officially inaugurated.
The BBC's Duncan Kennedy in Mexico City says the event is largely symbolic but will prove a psychological boost to Mr Lopez Obrador's supporters who believe he was cheated.
The campaign hopes to spend the next six years opposing the rule of Mr Calderon.
Some commentators say the "election" of a parallel administration will help reduce the possibility of radical street demonstrations.
One supporter, Lidia Alvarado, said: "It is going to be very rough for Calderon. Wherever he goes, we'll be there to remind him he became president through fraud."
The protesters had occupied the Zocalo since the election seven weeks ago but agreed to disband the tent city for good ahead of Saturday's military parade.
President Fox reviewed thousands of military personnel in the Zocalo at the parade.
But small groups of Lopez Obrador supporters held up signs reading "Fox, crook" and "Vote by vote".
Their campaign has been based on a call for a full recount of the vote.
Others at the parade cheered Mr Fox and president-elect Mr Calderon, who is from the president's party.
On Friday Mr Fox moved Independence Day celebrations out of the capital amid security fears.
He gave "el grito" - the independence cry of "Viva Mexico!" - from the town of Dolores Hidalgo, 270km (170 miles) north of Mexico City, where in 1810 national hero Miguel Hidalgo established the movement for independence from Spain.
A government spokesman said the event was moved from Mexico City because of fears of radical groups planning violence.