Former President Nestor Kirchner of Argentine has announced he will resign as the head of the country's ruling Peronist party.
The party has recorded heavy losses in mid-term elections on Sunday.
Mr Kirchner finished second in a high-profile race, defeated by a millionaire from a rival faction within the party.
His wife, President Cristina Fernandez, whose economic policies were unpopular, also lost her majority in Congress.
The BBC reports Sunday's mid-term polls were seen as a referendum on the presidential couple who have dominated Argentine politics for the past six years.
Mrs Fernandez, who succeeded her husband as president in late 2007, has seen her popularity fall amid the country's worsening economic problems.
She brought forward the elections, which were originally set for October, arguing that this would then allow the country to unite to face the global economic crisis.
Despite the election outcome, she ruled out a Cabinet reshuffle on Monday.