52-year-old Savitaben Khant was yesterday declared elected from Morva Hadaf Assembly constituency in Panchmahal district.
Ms Khant was at the counting centre yesterday when she felt giddy and fell off the chair. She was rushed to a hospital in Godhra, the district headquarters of Panchmahal.
After her condition deteriorated, the Congress leader was shifted to a private hospital in Vadodara, about 100 km from Godhra. She was kept on ventilator but died around noon, her family said.
Ms Khant, a resident of Viramiya village, had defeated her nearest rival Bijalbhai Damor of BJP by a margin of 11,289 votes in the newly-formed constituency. Tragically, she was unaware of her victory till she breathed her last.
Her supporters rushed to the hospital here after learning about the illness.
Ms Khant's body will be taken to Godhra to enable the party workers to pay their respect before the last rites are performed, Panchmahal Congress leader Samarsinh Patel said.
With Ms Khant's death, the Opposition party's strength in the 182-member Assembly has been reduced to 60.