Akshay Bam pulled out of the race and switched over to the saffron party.
The Congress, ejected from the contest after its Indore candidate joined the BJP, is appealing to voters to press the 'None Of The Above' (NOTA) option, a move slammed by the ruling party as negative tactics.
Akshay Kanti Bam, who had been pitted against BJP's sitting MP Shankar Lalwani, shocked the grand old party on Monday, which was the last day for withdrawal of nomination after he pulled out of the race and switched over to the saffron party.
The Indore constituency in Madhya Pradesh will go to polls on May 13 in the fourth phase of the general elections.
"Voters of Indore had delivered a huge victory to the BJP in the last municipal and assembly elections. In spite of it, the saffron party murdered democracy by unfairly luring Bam. Voters must give a befitting reply to BJP by hitting NOTA," senior Congress leader Shobha Ojha told PTI on Thursday.
MP Congress chief Jitu Patwari had said on Tuesday that his party won't support any candidate, adding that voters had NOTA option to punish the BJP.
Congress leaders' "instigation" of voters to use NOTA shows that the main opposition party is resorting to "negative tactics" in the festival of democracy, said Lalwani.
The BJP has been on a winning streak in MP's commercial capital for the last 35 years.
Indore, the largest constituency in the state in terms of electorates, has 25.13 lakh eligible voters. BJP leaders have claimed that the party is aiming to win the Indore seat by a margin of 8 lakh votes this time.
During the 2019 elections, Mr Lalwani defeated Congress' Pankaj Sanghvi by 5.48 lakh votes. NOTA had polled 5,045 votes then.
After the withdrawal of nominations, 14 candidates, including nine independents, are left in the fray in Indore.
"The option of NOTA is not good for democracy. Voters must choose one of the candidates," said Abhay Jain, who is contesting as an independent.
Mr Jain heads the Janhit Party, formed by former RSS workers. The party is yet to be recognised by the Election Commission. Janhit Party is promising to "free Indore of drugs and money and muscle politics".
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)