They retained three of the five seats in Modi's constituency Varanasi by comfortable margins and wrested the remaining two from the Samajwadi Party.
In an electoral performance that may have surpassed all expectations, the alliance ended up winning three other assembly segments falling under Varanasi district, wresting two of these from the BSP and one from the Congress-SP combine.
In the city, sitting MLA Ravindra Jaiswal retained Varanasi North, defeating former legislator and Congress candidate Abdul Samad Ansari by a margin of 46,000 votes.
Varanasi (Cantt) saw another successful debut, as Saurabh Srivastava won by a thumping margin of more than 60,000 votes to retain the seat that has been represented alternately by his late father Harish Chandra Srivastava and mother Jyotsna Srivastava.
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The BJP sprang a surprise in the predominantly rural Rohaniya, where Modi had held his last election rally.
The BJP's ally Apna Dal (Soney Lal) tasted victory in Sevapuri, where it was the runner-up five years ago. The party's Neel Ratan Singh Patel defeated sitting SP MLA Surendra Singh Patel by 49,000 votes.
Three more seats falling in the district -- Ajagara (SC)
and Shivpur forming a part of Chandauli Lok Sabha constituency and Pindra under Machhlishahr, were also bagged by the BJP-led alliance.
Ajagara was won by Kailash Nath Sonkar of Suheldev Bharatiya Samaj Party (SBSP) defeating nearest rival Lalji Sonkar by 21,000 votes, while sitting BSP MLA Tribhuvan Ram finished a distant third.
The SBSP is a breakaway faction of the BSP, floated by former Mayawati loyalist Om Prakash Rajbhar. The party had contested 52 seats in 2012 assembly polls, losing all and forfeiting deposits in 48.
In Pindra, the Congress-SP alliance came in for a rude shock as sitting MLA Ajay Rai suffered a humiliating defeat, finishing way behind BJP's Avadhesh Singh who beat the runner-up -- BSP candidate Babulal -- by a margin of 37,000 votes.
Rai, who was also the Congress candidate from Varanasi against Modi in the Lok Sabha polls, had begun his career in the 1980s as a BJP MLA from the now-abolished Kolasla.
After winning the seat three times in a row, Rai quit BJP in 2009 upon denial of a ticket for Lok Sabha polls, and fought the parliamentary elections on a Samajwadi Party ticket. After losing the LS polls, he won back Kolasla in the assembly by-poll that followed his resignation from BJP and joined the Congress before the 2012 assembly polls and won from the newly-created Pindra.