The amalgamation of charges into one coherent whole of corruption posed a serious challenge to Mamata who initially tried to brazen it out, but later realized that the strategy isn't working.

For the first time since the Narada sting tapes sprang into public consciousness, Mamata Banerjee on Sunday made a stunning admission. She said that had the tapes emerged earlier, she wouldn't have given party tickets to tainted ministers, many of whom have since recorded a sudden spike in blood pressure.

"An illegal company had done this in 2014, why bring this up now after the elections have been announced and candidates declared? Had it been earlier, I would have thought about it. Nothing can be done now. I cannot change candidates after announcing their names," said the TMC supremo at an election rally in Bowbazar area of central Kolkata on Sunday evening.

"We will launch our own probe and prove who were behind these tapes, and if anyone of our party is guilty, we will certainly take action against them," added the Chief Minister, referring to the tapes where several top TMC leaders and lawmakers were seen allegedly accepting bundles of cash in return for favours to be granted to a fictitious firm.

It couldn’t have been easy for the Chief Minister to virtually admit the authenticity of the videos which she and her party had dismissed earlier as "doctored" by the "dirty tricks department" of political rivals and a "cheap attempt at a smear campaign". In recent rallies, Mamata has also alleged "foreign money" behind the sting operation and questioned the credibility of journalist Mathew Samuel, the chief of Narada News.

Incidentally it is the same Mathew Samuel, then associated with Tehelka, who in 2001 had carried out Operation West End which showed political leaders, including then BJP president Bangaru Laxman, accepting bribes from journalists posing as defence dealers. Mamata Banerjee and her nine TMC MPs had walked out of the Atal Bihari Vajpayee-led NDA cabinet following that expose and struck an alliance with Congress ahead of the 2001 Assembly polls in the state.

It is this dichotomy that Narendra Modi has harped upon this polling season asking why is the TMC chief, who had quit the government at the Centre claiming moral high ground in 2001, now reduced to defending sting-tainted leaders.

"Why have you suffered such a 'poriborton', Didi? Does it mean you have adjusted to corruption?" Modi has asked of her during all of his election rallies in the state.

Mamata, it seems, has been forced into this admission for three reasons. One, it is becoming increasingly clear that the weak defence of "doctored videos" isn't cutting much ice with the electorate. Visuals have a stunning impact and the CM fears that news channels showing in loop TMC leaders purportedly accepting thick wads of cash is bound to adversely impact voters at the eleventh hour of polling.

Second, by its very nature, videos compel more attention and have better stickiness. The Narada sting lent visual imagery to corruption scandal that started with Saradha. The probe into chit fund scam generated a lot of initial interest, but the CBI's tepid progress had eventually taken the edge off it. The sting videos were perfectly timed to solidify the corruption charges and made graft an opposition poll plank, much to the dismay of the ruling party.

On Sunday, during a rally on Shaheed Minar ground in Kolkata, the Prime Minister sought to link the Sarada, Narada and Kolkata flyover collapse. "Look at the people in the Sarada scam. You will find the same people getting caught in the Narada sting. And again these very people are linked to the flyover collapse."

The amalgamation of charges into one coherent whole of corruption posed a serious challenge to Mamata who initially tried to brazen it out, but later realized that the strategy isn't working.

Last but not the least, incorruptibility is Mamata's biggest political capital. The swirling mud of Sarada scam which left a splash on many TMC leaders and even some of the Left Front, failed to taint Mamata. Amid widespread allegations of corruption and the meteoric rise of the infamous 'syndicate culture' during her tenure as Chief Minister, no one has been able to point a finger directly at her. It is this conviction, that people in the state still believe her to be honest even if they don't trust her party colleagues, led her to declare herself as the "sole candidate in all 294 seats".

Even as an administrator, Mamata has been able to retain the impression of a "street fighter" to go with her carefully constructed "uncompromising crusader against corruption" image. Heading a personality-centric party, she cannot afford to take even the slightest of hits to her integrity or risk an erosion to her political capital. It is this compulsion that may have forced Mamata's hands into abruptly pulling the rug from under the feet of her party colleagues who on Sunday were either busy offering "no comments" to Didi's change in stance or refusing to even take a phone call from journalists.

Sovon Chatterjee, city mayor and candidate from Behala (east) constituency, one of the TMC leaders caught allegedly pocketing cash in the Narada videos, said he isn't aware of the party chief's comments. "I can't comment on something I am not aware of. If at all, I'll give my statement to the party, since the TMC has already ordered an internal probe," he was quoted, as saying in Bengali daily Ei Samay.

Subrata Mukherjee, state minister for public health engineering and a candidate from Kolkata's Ballygunge seat, said he is not ready to offer any comments while urban development minister Firhad Hakim, whose name has been linked to the Vivekananda Road flyover collapse, did not give a reaction either.

The Lok Sabha Ethics Committee has sent notices to five TMC MPs caught in the scandal while the Kolkata High Court has set up a three-member panel to collect unedited footage from Narada's Delhi-based editor Samuel. The wheels are moving.

And it is this, say opposition leaders, that has forced an admission from the Chief Minister.

Surya Kanta Mishra, CPM leader and CM candidate of the Left Front-Congress alliance, tweeted that it is "too late for Mamata to escape".

CM trying to disown her tainted party leaders to save her own skin in Narada. Its too late for you and them to escape, Madam! — Surjya Kanta Mishra (@SurjyaKMishra) April 17, 2016

"There is still enough time for the Chief Minister to cancel the candidature of the tainted leaders and file a fresh list. Who is stopping her? The point is that she is not serious about the charges and is indulging in mere theatrics to gain public sympathy. This is a late, desperate attempt to salvage a situation but unfortunately it won't have any impact. People of Bengal have made up their minds to boot her out," said MP and state Congress president Adhir Chowdhury to 24 Ghanta, a local TV channel.

"By abandoning her party colleagues as the eleventh hour, Mamata Banerjee is trying to at least save her Bhawanipore Assembly seat," said CPI (M) MP and candidate from Jadavpur Loksabha seat Sujan Chakraborty. "She admits that what she did is wrong, yet she wants votes from people. Why should voters oblige her?"

Ex-BJP state president Rahul Sinha, BJP's candidate from Kolkata's Jorasanko area, said: "If Mamata Banerjee cannot drop leaders from candidates' list because it is too late, why isn't she taking action against those leaders who are not contesting in the polls? Why is she still giving a party ticket to Madan Mitra who has been jailed for corruption? She is in a spot and is trying to bluff her way out of trouble."

The Narada videos threaten to become the TMC's Achilles' heel.