Sergio Massa marches down a corridor, casting aside his suit jacket and rolling up his shirtsleeves – as if preparing for a schoolyard tussle – before facing the camera: “If they want to fight, we’re going to fight,” he says.
 
That’s the controversial TV spot Mr. Massa, who is running for a congressional seat in Argentina’s upcoming midterm elections, chose for his campaign. But he is not the only politician to adopt an aggressive tone against the Front for Victory, President Cristina Fernández de Kirchner’s ruling alliance.
 
“Her or you” is lawmaker Francisco de Narváez’s polarizing slogan. Meanwhile, the Front for Victory has implored voters to “choose love over hate” in today’s open primaries – in effect a mass poll for the decisive midterms on Oct. 27. The results will determine Kirchner’s level of support after a turbulent year of mass protests and unpopular economic policies.
 
The campaigns lay bare a widening fissure here between government supporters and critics that some warn could lead to long-term social and cultural divisions. “The polarizing dynamic has become impossible to control,” says Atilio Borón, a political author and sociologist in Buenos Aires.

Argentina is divided today into kirchneristas – people who back the leftist policies of President Kirchner and her late husband and predecessor, Néstor Kirchner – and anti-kirchneristas. Very few occupy a middle ground.
 
“When interests clash, you’re forced to take sides,” says kirchnerista Mariana Itzkovich at a recent rally to celebrate a decade of Kirchner rule. Echoing other populist governments in Latin America, Kirchner casts groups with “economic interests” and “corporations” as enemies trying to topple her administration or halt its reforms.
 
Another Front for Victory slogan written across campaign posters is “choose people and not corporations.” Voters are seemingly presented with a simple choice of “with us or against us.”

“Fomenting division suits Kirchner,” says Carlos Germano, a political analyst here. “She has a strong nucleus of support – around 30 percent of Argentines. But no opposing party or alliance has yet capitalized on the rest of the country, which remains split – though Massa is now establishing himself as the figure in Buenos Aires province.”
 
That is reflected in the lack of allegiances among government critics. “I don’t know who I’ll vote for,” says Amadeo Rodríguez at a small anti-Kirchner rally in Buenos Aires Thursday night. “All I know is it won’t be for Front for Victory candidates.”
 
The political polarization is reflected both socially and culturally: Mr. Rodríguez says he has friends in opposing camps who have become distant and knows families that have fractured. The media, meanwhile, is split between extreme pro- and anti-Kirchner coverage, the latter of which is led by the Clarín group.
 
Collecting an award this week, Jorge Lanata, Clarín’s best-known journalist, warned that the “crack” in society will transcend the Kirchners. “The social gap is going to be the hardest thing to mend,” Mr. Lanata says. He adds that a similar division was present during the first government, from 1946 to 1952, of Juan Domingo Perón – one that lives on in today's Argentina.
 
Like Kirchner, Perón – who was a hero of the working class – split the country into supporters and detractors, known as gorilas. Perón “divided Argentina into two irreconcilable subcultures,” the editors of The New Cultural History of Peronism, wrote.

Some politicians, though, have now decided to attract voters through a call for unity. “We've come to unite a country” is the slogan for congressional candidates of the Progressive Front.

 Kirchner lost control of Congress in the 2009 midterms, but Mr. Germano does not expect a repeat. “The Front for Victory will keep its majority,” he says. However, Kirchner is not expected to gain the seats necessary to push through long-rumored plans for constitutional reform and the subsequent lifting of presidential term limits.