Thousands of Argentines are protesting against the government headed by President Cristina Fernandez.
The campaigning for the elections ended yesterday amid a huge and deadly gas explosion in Rosario that prompted politicians to cancel the final campaign rallies and deflated the protesters' plans.
"Let's shake things up" was the theme of the marches, taken from Pope Francis' speech to Argentines in Rio de Janeiro. Their signs condemned corruption, inflation and unchecked presidential power.
Martin Insaurralde who leads the ruling party's slate for congress said that the government's opponents are proposing plans that have proven to be failures.
The voting will take place on Sunday.
