If the unions cannot be tamed, Mr Peña's other reforms to open up the monopolised energy sector and overhaul the tax system may be similarly diluted.The runner-up in the election was the left-winger Andrés Manuel López Obrador, known as AMLO, who came a very close second to Mr Calderón in 2006 but lost to Mr Peña by 6.8%.
The left has about a quarter of the seats in Congress, but many of its congressmen have little patience with AMLO, whose magnetic personality repels as many voters as it attracts.The government may also face opposition outside Congress.
It is now capable of summoning large crowds via Twitter and Facebook to march against Mr Peña (and often, it seems, for AMLO).
Milenio leads with "Vázquez Mota puts on the gloves"; El Universal says "Peña and AMLO, cautious; JVM attacks".
La Jornada's front page is neutral, but the story inside dismisses Ms Vázquez, saying that the debate "leaves AMLO and Pena as the finalists".
Mr López Obrador, known to friends and foes alike as AMLO, is still a polarising figure.
Last week, Mr Lopez (or AMLO as he is known) announced that he is hiring the Giuliani group, the consultancy formed by the former New York mayor, to advise on cutting crime.AMLO is not giving up any of his budget for this unlikely venture.
"There are voters who would consider the left as an option, but not with AMLO".For that reason, many PRD leaders preferred Marcelo Ebrard, the moderate mayor of Mexico City.
Following an inquiry by the Thai Anti Money Laundering Organisation, Amlo, a court in May 2014 ordered her to hand over $35.6m as the proceeds of crime.
Carolina, who affectionately refers to Lopéz Obrador as "AMLO," has registered to vote so that she can cast a ballot for him and she's joined a broader effort to persuade other Mexicans in the U.S. to register, too.
"I would be surprised if this year the majority of Mexican voters abroad don't vote for AMLO," Sarukhán told me.
