Shares of MercadoLibre (MELI), Banco Macro (BMA), Central Puerto (CEPU), Despegar.com (DESP), Grupo Financiero Galicia (GGAL), Loma Negra (LOMA), Pampa Energia (PAM), Telecom Argentina (TEO), YPF (YPF), Arcos Dorados (ARCO) and Vista Oil & Gas (VIST) are under pressure on Monday after Argentina’s President Mauricio Macri lost a primary election over the weekend. The pro-business Macri lost by a far greater margin than expected on Sunday, casting doubt over the incumbent’s re-election chances in October.

MACRI LOSES PRIMARY: Argentina's President Mauricio Macri, who is known for being pro-business, lost a primary election on Sunday. In a nationwide primary, Macri received 32% support versus 47% for his opponent, Alberto Fernandez, with more than 80% of the ballots counted, the government said, according to the Wall Street Journal. Fernandez is a member of the Peronist movement whose vice-presidential running mate is ex-President Cristina Kirchner, the "firebrand nationalist," according to the publication. The primaries are seen by many as a key gauge for the first round of Argentina's presidential elections on October 27, with many now fearing that the country is ready to reject the ruling government's economic policies. Argentina's peso has shed around 25% of its value to around 60 per U.S. dollar shortly after the open of trade.

PRICE ACTION: In morning trading, shares of MercadoLibre have dropped about 10%, Class B shares of Banco Macro have plunged over 52%, Central Puerto and Grupo Financiero Galicia have fallen over 50% each, Despegar.com has slid over 25%, Loma Negra has dropped almost 59%, Pampa Energia has plunged over 55%, and Telecom Energia has slipped almost 32%. Also lower are YPF, Arcos Dorados and Vista Oil &Gas, sliding 31%, 11% and 3%, respectively in early trading.