Bhardwaj, who contested the 2009 Lok Sabha elections on a BSP ticket and was the richest candidate with assets worth over Rs.603 crore, was gunned down in the farmhouse in south Delhi's Rajokri area around 9 a.m., an official said.
He was rushed to Army's Research and Referral Hospital where he succumbed to injuries.
His associate was injured and is under treatment.
Initial inquiries revealed that the killers entered the farmhouse in a black car with a fake registration number. There was a heated argument after which they shot Bhardwaj and fled from the spot.
Bhardwaj, 61, who dabbled in real estate, hotels and education, was rushed to Fortis Hospital in Vasant Kunj where he was declared dead.
Police said three to four rounds had been fired from an automatic revolver. Bhardwaj suffered three bullet injuries, an official said.
Prima facie, it appears to be personal rivalry, he said, adding that the men might be contract killers, hired to do to the job.
The car is yet to be traced.