The winner of Mexico’s presidential election was finally declared last week, when a tribunal unanimously dismissed a legal challenge to the results of the July 2012 vote. The decision ushers back into office Enrique Pena Nieto’s Institutional Revolutionary party (PRI), which until 2000 had held the presidency for 71 straight years.

But the elections ignited a powerful protest movement across Mexico, calling for an end to politics as usual. And that movement is here to stay.

Buying votes, buying elections

The PRI's 71 years in power were marked by allegations of corruption and vote-rigging. Although their leader, Pena Nieto, insists they have changed, leaked cables surfaced in June revealing that Mexican media giant Televisa – which controls 70% of television programming in the country – made millions of dollars selling the PRI's politicians favourable coverage.

These reports, along with early allegations of paying off voters, led to mass demonstrations. The student-led movement Yo Soy 132 called for media and electoral reform, claiming that Pena Nieto enjoyed unjust advantages from media outlets, pollsters and campaign donors.

The initial results of the 1 July election put Pena Nieto in the lead by 6.5 percentage points. But he was immediately accused of buying votes – up to 5m of them – by rewarding voters with supermarket gift cards, fertiliser, cement and even livestock. Leftist leader and presidential runner-up Andres Manuel Lopez Obrador filed a legal challenge to the results, citing widespread fraud.

Will the movement march on?

In July, Avaaz joined countless other campaigners and citizens to launch a petition calling on the electoral tribunal to carry out an objective, transparent and thorough review of the elections. Almost 60,000 signatures were delivered directly to the court on the eve of its decision. Yet on 30 August the tribunal dismissed the challenge, labelling the election "free and democratic" and paving the way for Pena Nieto's inauguration in December.

Immediately, demonstrators gathered and Obrador defiantly declared that he would not accept the ruling, calling for a rally in Mexico City on 9 September.

The PRI is preparing to take power once again, but this powerful new protest movement continues to call for change: for cleaner, fairer politics. Some claim that now the winner has been declared, its power and appeal among the Mexican public will wane, but others believe the outcry will force the PRI to shift its political priorities and confront issues of corruption and political reform head on. One thing is for sure: only by keeping up the pressure can this new movement help to usher in a new era of fairer, cleaner democracy in Mexico.

Read more: The Guardian has an excellent, detailed expose of the PRI's cosy relationship with Mexico's media.

Sources: Guardian, Reuters, Avaaz, Wall Street Journal, AP