That last claim can be hard for some to stomach given the pair's history.
Fernández, who will take office in December, first became cabinet chief in the government of Fernández de Kirchner's late husband Néstor, from 2003-07.
The Frente de Todos leader maintained the role when Fernández de Kirchner' succeeded her husband but quit a year later over her tough handling of a dispute with farmers over an increase in taxes on agricultural exports.
Undoubtedly, though, Fernández de Kirchner' remains the biggest heavyweight in Argentine politics, despite the embarrassment of being implicated in a dozen corruption investigations.
She has already gone to trial in the first of those and only her parliamentary immunity – she's currently a senator – is keeping her out of pre-trial detention.
A clue as to who really has power may come in the following key days when the configuration of the new government will be decided.
Fernández de Kirchner' is heading to Cuba to be with her daughter Florencia, who is undergoing treatment there for health problems, and will not return until November 11.
For some, it's a situation that resembles that in Russia when Vladimir Putin reached the end of his stipulated two terms as president in 2008, only to switch to the secondary role of prime minister for four years before returning as president.
In the meantime, current Prime Minister Dmitry Medvedev – Putin's campaign manager from his 2000 election victory – kept the president's seat warm.
Political analyst Raúl Aragon says this simply won't be the case as headstrong 60-year-old lawyer Fernandez could never be a "puppet."
When he was her cabinet chief, "Cristina couldn't control him then, much less so now."
That doesn't stop some from believing Fernández de Kirchner will be in command, but the number is decreasing.
"In the collective imagination there's a portion of the population that believes Cristina will govern and others believe it will be him," said sociologist and consultant Ricardo Rouvier.
"But in recent days, the proportion that believes it will be him has grown. They view him as more at ease, with greater media presence, more autonomous."
Many analysts praise Fernández de Kirchner' for a brilliant strategy in designating Fernández to lead the Peronist movement.
He managed to reunite the divided strands of Peronism during the election campaign.
"One day, Cristina rang me and said: now it's your turn," Fernández said at his final campaign rally. "Thanks, Cristina for the show of faith."
It might sound like Fernández de Kirchner' is still pulling the strings, but Rouvier insists Fernández is in charge.
"I don't see a dispute that could endanger governance."
Fernández has vowed to change the country left behind by Macri, with yearly inflation of 55 percent, poverty at 35 percent, drained Central Bank reserves and a record external debt.
He's already taken part in the renegotiation of a US$10 billion debt to the International Monetary Fund in 2005, but will have to do so again with Argentina having secured last year a US$57 billion bail-out package.