Fernandez failed the first electoral test of her second term on Sunday as ruling party candidates trailed opponents across Argentina's most populous provinces, but far from admit defeat, she urged her followers to redouble their efforts. "We're going to keep deepening this transformation, because it's our obligation," she said.
"There may be other politicians showing up offering something different," she added. "I ask that all of you think about what we've done in the last 10 years."
The governing Front for Victory party remains the only political force in Argentina with a nationwide organization, and got the most votes Sunday in six of seven provinces with senate races. But its house candidates got the most votes Sunday in only eight of the 23 provinces, and trailed in every major city, including the capital and the all-important surrounding province of Buenos Aires, a traditional Kirchner stronghold, where 35 per cent of the voters live.
With 52 per cent of the vote counted in the suburbs around Argentina's capital, Sergio Massa's Renewal Front was leading the president's hand-picked candidate, Martin Insaurralde, by 34 per cent to 29 per cent.
And Massa, who broke from Fernandez only 40 days before the primaries, sounded more like a presidential candidate than a campaigner for the house of deputies in his victory speech. He invited people from all over Argentina's polarized political landscape to join him in a new movement that would rule from the centre, build coalitions and protect the middle class, a group that he said hasn't been represented.
"We have to think of the future. We have to learn to stop looking at the past as a way to build a future for all Argentines," Massa said. "We feel proud that the path we have chosen is one of unity in diversity, of coming together without aggression ... the people who have joined us are saying 'enough with confrontation in Argentina."
Insaurralde, a 43-year-old mayor of Lomas de Zamora, was hand-picked by Fernandez and showered with attention as she sought to improve his name recognition. She even brought him to Rio de Janeiro for a photo-opportunity with Pope Francis.
Massa, the 41-year-old mayor of the wealthy riverfront Tigre municipality, briefly served as Fernandez's Cabinet chief and now leads a breakaway branch of Peronism, the broad and splintered political movement that many Argentines claim some allegiance to.
Fernandez won re-election nearly two years ago with 54 per cent of the vote, but her popularity has dropped since then amid corruption scandals involving her appointees and close allies, growing discontent over inflation, deteriorating public services and what many see as a weakening of the nation's institutions in the face of authoritarian presidential power.
Sunday's vote was Argentina's first obligatory nationwide primary, but most parties settled on "pre-candidates" beforehand and presented unified slates, turning the election into a party-popularity contest ahead of the Oct. 27 vote.
With half the seats in congress and a third of seats in the senate up for grabs, the results could determine whether Fernandez will have new checks on her power. For now, she doesn't need the votes of any opposition lawmakers to provide the quorums she needs to push through legislation or quash investigations.
If her opponents firmly control at least a third of the seats, they also could end any chance of changing the constitution to eliminate the two-term limit on presidencies. Whoever wins big in October could then become a leading candidate to succeed her in 2015.
Fernandez took the stage with Insaurralde and other ruling party candidates and then did all the talking at the post-election rally, warning Argentines not to trust politicians who make promises they can't keep.
"My great responsibility as president is to provide governability to Argentina," she added. "Don't expect me to promise things we can't provide. Because we have to rule in a complex world. That's not to say we're the most intelligent or the best, by God, we're human; we make mistakes. But we don't promise what we can't provide."
Associated Press writer Debora Rey contributed to this report.