Mangal Patwa, 50, who was BJP's Neemach (MP) district president, died while his niece Awanti (25) and the driver Vishnu were injured in the mishap.
Patwa was on his way to Udaipur when his vehicle was hit by the dumper in Nikumbh area of Chittorgarh, bordering MP.
They were rushed to a nearby hospital where doctors declared Patwa brought dead, Nikumbh police station SHO Bhagwan Lal said.
Later, the injured have been shifted to the Udaipur hospital, where their condition was reported to be stable, he said.