In the weeks preceding the conflict, Kiir's oponents within the SPLM had become increasingly critical of his failure to allow a meeting in which the top members of the party could elect a new chairman ahead of the 2015 elections.
Kiir, who has been chairman since the death of John Garang in 2005, was expected to be challenged by Riek Machar, suspended SPLM Secretary General Pagan Amum, and Garang's widow Rebecca Nyandeng.
"How many times did the detained politicians and the former vice president call for peacefully demonstration in the country, but Kiir himself disagreed with them because he knew that he has lost 100% support from the top party?" asked the rebel spokesman.
Gew said that the violence against civilians in Juba had forced many high ranking officials from the government and army to break away from Kiir's leadership.
A member of Unity state's parliament, who wished to remain anonymous, said that President Kiir should "tell the truth" about what happened in Juba during the first days of the conflict.
Those opposing Kiir say that by appearing in military fatigues and accusing Machar of staging a coup, he was attempting to use the army infighting to silence his critics.
The UN estimates that at least 1,000 people and nearly 200,000 have been displaced over the last three weeks of the conflict.