The incident took place shortly before BSP supremo Mayawati's arrival at the rally venue.
Addressing the huge gathering, Upadhyay appealed people to vote for the party and suddenly started weeping, saying: "I am working too hard in theses polls. For the last two months I wake up at 5 AM and go to bed by 2 to 3 in the morning."
"Once I slipped in the toilet and my head was hurt badly," he said. Some other party leaders who were present at the dais came to his rescue and consoled him.
"I am very confident of my win in the elections. If Congress comes to second number, I would then quit politics," Upadhyay promised to people.
The BSP candidate also came down heavily on BJP and said "I would bury BJP".
"BJP president Rajnath Singh ran away from Ghaziabad fearing his defeat and is now contesting elections from Lucknow. BJP has now fielded V K Singh, who is an outsider. By my win, I will bury BJP," Upadhyay said while addressing rally.