SP supremo Mulayam Singh's grand nephew Tej Pratap was leading over his nearest rival BJP's Prem Singh Shakya in Mainpuri Lok Sabha.
"While SP is leading in six seats, BJP and its ally in four seats and Congress in one," an Election Commission official said here.
The Assembly seats where bypolls were held include Saharanpur city, Bijnor, Thakurdwara, Noida, Nighasan Lucknow east, Hamirpur, Charkhari, Sirathu, Balha and Rohania, as also in Mainpuri Lok Sabha seat which was vacated by SP supremo Mulayam Singh Yadav.
Stakes are high for BJP, Congress, Samajwadi Party in Uttar Pradesh after the saffron party's near-total sweep of the 80 seats in Lok Sabha polls just four months.