The president's detractors were angered by his refusal to quit at the meeting he had with the ANC Top Six leaders on Sunday night.
Although ANC president Cyril Ramaphosa said he had began direct discussions with Zuma on the transition, yesterday the ANC in Western Cape said Zuma should have vacated his office already.
In an unprecedented move earlier Tuesday, Speaker Baleka Mbete announced that SONA would be postponed on request from opposition parties who have threatened to disrupt the proceedings.
A source in the NEC said the "sands have shifted" and the Zuma group will not succeed.
"(But) the caucus has not discussed the matter", he added.
They are now going for the kill, emboldened by the postponement of the Sona, which Zuma and his supporters - including ANC secretary-general Ace Magashule - were adamant that he would deliver the Sona tomorrow.
Analysts Dumisani Hlophe and Somadoda Fikeni agreed that allegiances were shifting towards Ramaphosa and noted that Zuma die-hards in the ANC top six, the ANC Women and Youth Leagues as well as the Umkhonto we Sizwe Military Veteran's League have fallen silent about his removal.
"The South African Communist Party condemns tribalism in the strongest terms possible and the ethnic mobilisation, including that of Amabutho (Zulu regiments) that President Jacob Zuma has apparently engaged in as part of his plan to continue overstaying his welcome in office".
"It is upon the ANC to take disciplinary action against any member who refuses to carry out a political instruction of the party".
"Zuma is increasingly isolated but the ANC's apparent reluctance to resort to parliamentary procedures to get rid of him and rather negotiate his exit appears to be playing into his hands", said Mike Davies, the founder of political-advisory company Kigoda Consulting. Zuma allegedly told them he wasn't "convinced" of their reasons for him to step down. Instead of talking about the transition, the officials went to tell Zuma to leave.
It's understood there are a few outstanding issues have been under discussion.
It was also announced on Thursday afternoon that the annual Ubuntu Awards had been postponed until further notice.
The South African Communist Party (SACP) had earlier accused Zuma of wanting to axe his deputy Ramaphosa, and further accused the embattled head of state of engaging in risky "ethnic mobilisation". "The allegations of ethnic mobilisation by the President are equally without foundation". Bongani Ngqulunga, Zuma's spokesman, said he was in a meeting and couldn't immediately comment.