A controversial demonstration of the Electronic Voting Machine last week in Madhya Pradesh's Bhind district last week seemed to lend credence to the opposition's accusation that voting machines could be tampered with. It is a charge that the Election Commission has strongly rejected more than once this week. And now, a top poll panel official flown into the state to oversee by-polls to two assembly seats over the weekend has decided to hold 150 demonstrations to put all doubts to rest.