Chief Minister Mamata Banerjee is all set to win the crucial Bengal bypoll, with Sunday morning trends showing she is well ahead of her main rival from India's ruling Bharatiya Janata Party.

The 66-year-old firebrand woman politician is leading by more than 30,000 votes in the by-election for the assembly constituency of Bhawanipur in state capital Kolkata, the Election Commission of India has said.

Read: Crucial bypoll begins in Bengal to decide Mamata's fate

In Bhawanipur, Mamata has to pull off a win to continue as Bengal Chief Minister. BJP has pitted a little-known woman lawyer against Mamata.

Though her ruling Trinamool Congress party swept back to power in Bengal in April-May assembly polls, Mamata lost her own seat in Nandigram to her protege-turned-rival Suvendu Adhikari by nearly 2,000 votes. 

India's main opposition Congress, on the other hand, did not fielded any candidate against Mamata. The party's decision was announced by West Bengal Congress chief Adhir Ranjan Chowdhury earlier last month.

On May 2, Mamata single-handedly pulled off a landslide victory in the assembly election for the third time in a row, bucking anti-incumbency and staving off a massive challenge from Prime Minister Narendra Modi's BJP.

Read: Mamata to kickstart campaign for Bengal bypoll today

In June this year, Mamata moved the high court to declare Suvendu's election win "null and void' on the grounds that he had indulged in corrupt practices and sought votes on the basis of religion. 

Bengal had witnessed the most high-profile contest in India's recently held state polls. While Mamata harped on being Bengal’s daughter, the BJP asked people to vote for "change and development" after 50 years of Communist and Trinamool rule.