Mamata Banerjee and Congress's attempt at a 'marriage of convenience' in West Bengal could well be over after the Chief Minister announced on Wednesday that her Trinamool Congress would contest the upcoming Lok Sabha elections alone.

Ending the uneasy calm between the two INDIA bloc partners, Banerjee alleged that the Congress had "rejected all her seat-sharing proposals", adding that the Trinamool would contest all 42 seats in Bengal.

However, it was not a knee-jerk move. The situation had been simmering for the last two months; the discord over seat sharing came out in the open now and then.

It was exacerbated by state Congress chief Adhir Ranjan Chowdhury - a fierce critic of the Trinamool chief - who stepped up his attack against Banerjee, calling her an "opportunist" on one occasion and "dalal" on another.

The bomb eventually exploded on Wednesday, just a day before Rahul Gandhi's Bharat Jodo Nyay Yatra was to enter West Bengal

Congress's lack of clarity on Trinamool has never been a secret. While Mamata Banerjee shares a good rapport with Sonia Gandhi, the Bengal unit of the Congress, led by Adhir Chowdhury and Abdul Mannan, have been her vocal critics.

The Congress's dalliance with Mamata Banerjee at the national level has always made state Congress leaders uneasy. The state unit has always accused the Trinamool of weaning away its leaders and sees Mamata's party as the principal reason for its decimation in the state.

In fact, Adhir Ranjan Chowdhury was not in favour of forming an alliance with the Trinamool in the first place and wanted to go with the Left.

It's not that the Congress and TMC have not joined hands in the past. The two parties had previously allied in the 2001 Bengal Assembly election and the 2009 Lok Sabha polls. Importantly, the TMC and Congress alliance in 2011 led to the ouster of the CPI(M)-led Left Front government after 34 years in Bengal.

However, things were different this time.

The first sign of discord was when the Trinamool Congress reportedly asked Congress to contest on two of the 42 seats in Bengal, denying their request for at least 8–10 seats.