The accused identified as Atin Tiwari (40), was nabbed last night from a coffee house in Gita Bhawan locality, Superintendent of Police (East), O P Tripathi told reporters.
He also runs a fitness centre in the city, the SP said.
Associates of Tiwari had called few Congressmen in Indore claiming that they were experts in tampering EVMs (electronic voting machines) and assured that the party candidate from Agar, Rajkumar Gore can win the election, and demanded Rs 8 lakh from them, Tripathi said.
Bhopal-based Cyber Crime Branch is probing the matter in detail.
The polling for by-poll in three assembly seats including Agar was held on August 21 and the results will be declared tomorrow.