protesters Televisa
© Tomas Bravo/ReutersPolice and protesters outside the Televisa building in Mexico City.
Some brought tents and blankets and a few hugged guitars, but by far the most common accessory seen at the 24-hour siege of the broadcasting giant Televisa that began on Thursday were banners accusing the network of trying to "impose" Enrique Peña Nieto as president.

"Televisa: factory of lies," read one held up amid the rows of protesters that faced a wall of police officers around the building. "Weapon of mass manipulation" said another bearing a picture of a television. "Don't let Televisa put you to sleep," a third warned.

Mexico's student movement sprang up 10 weeks ago to thrust the issue of alleged media bias in favour of Peña Nieto to the centre of the presidential campaign.

The candidate won anyway, putting the revamped Party of Institutionalised Revolution (PRI) en route to regaining the power it had held from 1929 to 2000, and the students refocused their energies on rejecting the result of a poll they say was unfair.

But the sense that they are riding a new tide capable of shaking up the political and media establishment has begun to ebb away, and the palpable excitement that infused the early rallies is being replaced by expressions of frustration, anger and impatience.

"The movement started as a breath of fresh air as young people began to wake up," said Fernando Valenzuela, 21, a sociology student, as he prepared to spend the night at the Televisa picket. "Things are getting more radical now because the legitimacy of the institutions is running out and nobody wants to have to live with Peña Nieto as president for the next six years."

They will probably have to do so. Few observers expect the electoral authorities to accept that the evidence presented by the leftwing runner-up, Andrés Manuel López Obrador, who alleges vote-buying and dodgy campaign financing as well as media bias, is weighty enough to annul the outcome.

So what next for the students who call themselves #yosoy132? The name, meaning I am 132, is a reference to the number of students who made a YouTube video that first prompted the movement after Televisa downplayed a protest against Peña Nieto at a private university in May. There were 131 of them, so everybody else is now, symbolically, number 132.

Rachel Sieder, an expert in Latin American social movements, said the Mexican students and their social media-fuelled protests constituted a phenomenon somewhere between the Arab Spring and Occupy Wall Street. "It is not likely to transform the political system now, with the recent presidential election reinforcing old-style clientelistic politics," she said. "But it does signal a critical mass of young, soon-to-be professionals who are calling for a fundamental change in the prevailing political and electoral culture."

With the impact of their near-weekly marches beginning to wane, the largely middle-class movement has begun seeking a renewed lease of life through alliances with more traditional leftist social movements. Some of the students' most fervent critics celebrate this development as a sign that the movement will soon relegate itself to just another minority protest group with nothing new to offer. "They are throwing away the brand," said the advertising veteran and longtime PRI stalwart Carlos Alazraki.

There are further challenges in the need to juggle tensions between emerging leaders and the principle of consensus in all decision-making, the divergences of focus between students from private and public universities, and the difficulty of not looking like they are at the service of López Obrador's legal challenge.

The Televisa picket was a kind of return to the movement's roots, but this time the network was in no mood to launch the kind of damage-limitation exercise that ensured the first wave of protests were covered in detail. Its flagship news show dedicated the first half of its hour-long broadcast to the Olympics and included just a brief transmission of the scene outside its building towards the end of the programme. Televisa has submitted documents to the electoral tribunal backing its claim to have been completely neutral in the election, but it does not tend to answer the students' accusations directly on screen.

Hunched over their smartphones in a Mexico City cafe this month, members of the #yosoy132 media commission alleged they were constantly trying to hold off a "disinformation campaign" against them that diminished their importance and exaggerated their troubles, but stressed they did not need the traditional media to get their message across.

"We started as a hashtag and we became a movement," said Martha Muñoz, 19, a communications student. "We have thrown a ball up into the air. Now we have to see who catches it."