Minister of National Infrastructures Benjamin Ben-Eliezer and Agriculture Minister Shalom Simhon have already announced they will back Barak, and other Labor lawmakers are expected to follow suit.
In his campaign, Barak intends to focus on his qualities as defense minister, and present himself as the most appropriate person to restore the Israel Defense Forces at a critical juncture.
Aides of Labor Party Chairman Amir Peretz on Sunday dismissed the announcement, however, and highlighted Defense Minister Peretz's record of public service.
"Those who think that a 30-year record in public service will disintegrate as a result of wild incitement against Amir Peretz have another thing coming," they said.
In a letter sent to Labor party secretary-general, Minister Eitan Cabel, Barak wrote "The State of Israel, the Israel Defense Forces, and the defense establishment are in a very shaky situation. I believe that I have the experience and the maturity to serve as the next defense minister of the State of Israel."
Barak has so far avoided holding a press conference and opted to announce his return to active political life through a short letter in which he relates to his lack of maturity during his tenure as prime minister in the late 1990s.
"The decision was a difficult one. It is possible that I became prime minister too soon. I made many mistakes, and my lack of experience was to my detriment. Today I know that there are no shortcuts, certainly not in public and political life, and that leadership is a shared burden, not a solo mission. It is impossible to succeed alone and coherent thinking, will and talent on their own are insufficient to run a state," Barak wrote.
Barak, who is trying to lose the image of a forceful and scheming politician, which stuck to him during his first term as leader of the Labor Party, sent a message through his letter that he did not intend to take over the Defense Ministry through manipulation.
"On Friday I announced to Defense Minister Amir Peretz that I will not contribute in any way to any trickery and that I planned to run for the position of chairman of the Labor Party in the elections set for May 2007," Barak wrote.
Following his announcement Sunday, Barak has joined the current leader in the polls, Ami Ayalon, as the top candidate to win the Labor primaries in May.
MK Ophir Pines-Paz, who announced his intention to run in the primaries early last week, called on Barak to join him and be appointed defense minister under his leadership.
Ayalon, on the other hand, welcomed Barak's announcement and said that "Barak's entry into the race will allow a genuine and long debate" to take place.
However, Ayalon did express criticism at the way in which Barak pulled out of Lebanon and his record as a manipulator. Ayalon was also critical of the unwillingness Barak has shown in exposing himself to the public and in participating in serious public debate in recent years.
Essentially, Barak began his campaign several weeks ago, and stepped up his efforts during the past three days with the help of Ben-Eliezer who called for his appointment as defense minister. At the same time, others announced their support for Barak, in an act clearly coordinated with Barak's campaign. These include former leading Labor figures such as Moshe Shahal, Shimon Sheves and Avraham Burg.
The real turn for Barak occured during the first day of the second Lebanon war, as a result of the loss of public confidence in the leadership of Olmert-Peres.