Congressional elections in Argentina had been scheduled to take place on October 25 of this year. However, unexpectedly, President Cristina Fernández de Kirchner  announced she would send a draft law to the Congress with the purpose of moving these elections forward to June 28. Since the government party has majority in both chambers of Congress, the proposal is expected to pass. Most of the opposition parties have come out against the decision, but others have expressed that they would not have major problems in supporting the project.
According to Página Impar [es] , former president Néstor Kirchner , who happens to be the husband of the current president “was behind the decision to change the national elections date to the 28th of June, after a meeting with congressmen from his party”. The decision was made quickly, and the Chief of Government of the city of Buenos Aires, Mauricio Macri , also announced that the local elections would take place on June 28 making it a different date from the national elections. With the decision of the government, now both will happen on the same day.
According to Artepolítica [es] , the reasons for this change are the international economic crisis that is expected to worsen after August; and the elections in the city of Buenos Aires (where the government expects the opposition to divide its votes among several options) and in Santa Fe, where the Peronism is looking for a single candidate.
Brujipedia [es]  points out that:
Hace una semana Néstor Kirchner pensaba diferente. (…) A los gritos, Kirchner preguntó: “¿Por qué adelantan tanto las elecciones? ¿Qué le pasa a la burocracia política? ¿Tienen miedo de perder que separan las elecciones?”
One week ago Néstor Kirchner felt differently (…) Kirchner asked out loud: “Why are they moving the elections up so much? What's going on in the political bureaucracy? Are they scared to lose so they separate the elections?”
This comment refers to the decision of the government of the province of Catamarca that brought forward the elections to separate them from the nationals. Now, it's his wife's government that makes a similar decision. And in La Política al Poder [es] , they state that “the official argumentation is not convincing.” The reason for the change of the election date would be that:
el gobierno lo hace por que cree que le conviene y esto es más que suficiente, asume la iniciativa, cambia el escenario y los pone a todos a correr, por que el tiempo es poco, los 225 días faltantes para la elección se redujeron a 100…
the government is doing this because they believe it's good for them and that's more than enough. They take the initiative, change the scenery forcing everyone into a race, because time is short. The next 225 days before the election are reduced to 100…
Now, the draft law of the Argentine government will go to the Congress, where it must be approved in less than two weeks if it it wants to meet the electoral datelines.