Cristina Fernandez de Kirchner likes to be known as the "first citizen"
Mrs Kirchner promised change but also pledged to continue what she called the re-founding of the nation.
She announced her candidacy in July after President Nestor Kirchner said he would not be standing for re-election.
Polls say she has a good chance of victory in October but rows denting the government's image may also affect her.
In a speech in the city of La Plata, Mrs Kirchner promised more jobs and less poverty.
She said Argentina must overcome its culture of failure and provide its citizens with a sense of economic security.
She told supporters her husband had been responsible for rebuilding the democratic constitutional state, and for restoring the self-esteem of the nation.
Energy crisis
Mrs Kirchner does not like to be called "First Lady", preferring instead "first citizen", BBC regional analyst Martin Murphy says.
Many Argentines believe President Kirchner is doing a good job
She is a senator for the province of Buenos Aires and has her own political clout.
But having taken the place of her husband as the government's candidate for the 28 October election means that whatever the government does is reflected upon her, our analyst says.
As such, he says that the launch of her campaign does not come at a good time.
On Monday, the economy minister resigned after an investigation was ordered into the discovery of $64,000 (£31,000) in cash in the toilet in her office. She denied any wrongdoing.
Meanwhile, Argentina faces an energy crisis in the middle of one of the worst winters in the past 100 years.
Many Argentines believe the government is not doing enough to solve this crisis and they also complain about rising prices, even though government figures show inflation is under control.
But apart from these problems, polls suggest that almost half of the population believes President Kirchner is doing a good job.
According to official figures, since the economic crisis of 2001, unemployment and poverty have gone down, while GDP and public investment have gone up.
Mrs Kirchner's campaign will surely benefit from this, as well as from the lack of a united and strong opposition, our analyst says.
Here are some readers' reactions to Cristina Fernandez de Kirchner's decision to try to follow her husband into the top job.
I certainly do not believe that Mrs Kirchner is the right person to be leading Argentina at this point in time. She will be too heavily influenced by the ideologies and opinions of her husband. I think she should step aside and allow others in the party with fresh ideas and policies to run for the presidential elections.
Allister, Antigua & Babuda
I always worry when democracies start having dynasties getting elected to power. This is true in the US - the Bush family, the Clintons and Kennedys, or in Poland with the president and PM being brothers. Now Argentina is following suit. Are there really so few suitable candidates for election that these dynasties are formed?
Simon Murphy, Amsterdam
I think she is the right person to be chosen, I heard a lot about her. We should appreciate the decision.
Sumeet Barak, Pune, India
Cristina runs for president in order to make it possible to reign the country for 16 years! The corruption will start as of now. Nestor has not contributed much to the growth of the economy. Others probably would not do better. The reason for this is that this country is sick to the bone: Inefficiency rules, sticking out your neck is not appreciated, mediocre is good enough. Such a pity for such a rich country.
Arjen ten Have, Mar del Plata
As I understand it one person can be president in Argentina forever as long as they don't have a certain amount of terms consecutively. I think she is a puppet for her husband so he can continue his power hungry quest to rule.
Joshua, Chicago, USA
She launched her campaign to be able to go on with the increasing and totalitarian power they have got. As regards the numbers reflecting Argentina's improvement, not only are they manipulated by public organs such as Indec, but also are determined by world prices. In my opinion, she will not be able to deal with the situation, and, if we look back in Argentina's history, we can clearly see her term will finish as weakly as every second term of office we have passed.
Julian, Buenos Aires, Argentina
Female pretenders to the Argentine throne have left a questionable record at best. Irrespective of Mrs Kirchner's solid qualifications, the people would most likely prefer to see Mr Kirchner in office rather than vicariously by his wife.
Peter Polak, San Francisco, USA
Here in Mexico, the president's wife - Martha Sahgun - also tried to run for the presidency but, when rumours of her intentions were made public, she had to withdraw her candidacy because of accusations that she and her husband - president Vicente Fox- were trying to create a nepotistic government. I believe that successive terms in power by members of the same family is inadequate and (at least in Latin American countries) an invitation to corruption.
Epigmenio Ibarra, Mexico City, Mexico
I think it is great, it is not like she has stood in the background doing nothing. She is a senator for the state of Buenos Aires and she does have her own views and political goals. She is for reform and bettering the lives of those in Argentina. I think at the very least she should be listened to and taken as a serious contender for the seat in the Casa Rosada.
Luis Alberto Oviedo-Perez, Chicago, USA
Cristina Fernández de Kirchner
Current senator and Argentine First Lady Cristina Fernandez de Kirchner announced her presidential candidacy yesterday evening in La Plata, a city 50 kilometers (31 miles) away from Buenos Aires.

Mrs. Kirchner announced her intention to run for president at the ''Argentine Theatre'', the same location she used to start her 2005 campaign for the Senate as member of the Buenos Aires province delegation.

A large security detail was in place at the theatre and eight city blocks were closed to traffic for the event. Outgoing Argentine president Néstor Kirchner, members of his office, and provincial governors were present at the ceremony. Julio Cobos, governor of Mendoza and possible campaign team member, was also there.

Activists from Quebracho mobilized in La Plata to protest the candidacy of the First Lady, and created some disturbances near the event. None of the protesters was arrested, according to an official spokesman of La Plata Police Station.

Recent polls indicate that Mrs. Kirchner has at least 40 percent voter support, which bodes well for winning on the first ballot in the upcoming October elections.

According to Argentine newspaper ''La Nación'', this speech signifies that the government is attempting to show solidarity in the midst of recent scandals: Felisa Miceli's resignation to the Department of Economy after being accused of wrongdoing by a justice over the nearly $100,000 Argentine pesos and US$31,670 found in her office, and the alleged smuggling of weapons and irregularities in the office of the Secretary of Environment.