West Bengal Chief Minister Mamata Banerjee found herself on a collision course with the centre after a huge showdown on Sunday evening between the state police and officials of the CBI or Central Bureau of Investigation. The CBI officials, who had come to question Kolkata police chief Rajeev Kumar on two Ponzi schemes, were temporarily detained by the police. Accusing Prime Minister Narendra Modi and the BJP of political vendetta, a furious Ms Banerjee started an overnight dharna to "Save the constitution". While various BJP leaders have called for President's Rule in Bengal, opposition leaders have rallied around Ms Banerjee, making for a huge flashpoint with the centre.