LONDON, Sept 13 (Reuters) - Argentina’s bond markets rallied in early trading on Monday after the country’s Peronist government suffered a bruising result in primary elections over the weekend. Argentina’s main opposition party won key races in a congressional primary vote that is a strong indicator of how voters will cast ballots in the November midterm election. The most notable result was the Juntos opposition’s victory in Buenos Aires Province, usually a stronghold of the Kirchnerist-Peronist bloc. With 97% of votes counted, Juntos was ahead with 38% of the votes, a more than 4 point advantage. “The primaries results show strong punishment to the government, and demand for change,” U.S. investment bank JPMorgan said in a note. Investors reacted by pushing up the country’s benchmark 2035 dollar-denominated sovereign bond up as much 3 points traders said, on hopes the result would force the government, which has dragged its feet on an IMF programme, to address its economic problems. “If they (the government) are going to win back votes, the question is how are they going to do it,” said Ted Pincus at Switzerland-based fund manager Mangart which holds Argentine debt and was involved in last year’s restructuring. “In my view they will have to be more centrist because otherwise the currency is going to continue to weaken on the black market which will create more economic misery.” Political watchers say that if the result is repeated in the Nov. 14 midterm vote then the ruling party would lose their majority in the Senate and could lose their grip on the largest minority bloc in the lower Chamber of Deputies.