In fact, it was the by-poll here which was necessitated by Bachchan's resignation as MP in the wake of the Bofors controversy in 1988 which led to the emergence of two factors that changed the political landscape of UP.
First, Vishwanath Pratap Singh, who at the time had just resigned from Congress, won the 1988 bypoll defeating Congress's Sunil Shastri, the son of former Prime Minister Lal Bahadur Shastri.
VP Singh later went on to become the Prime Minister of India.
It was VP Singh's decision to implement the Mandal Commission Report which led to the emergence of the Other Backward Classes (OBC) as a very potent political force.
But the bypoll also marked the emergence of mercurial Dalit leader Kanshi Ram and his BSP as he surprised many by securing nearly 70,000 votes.